I'm reading in various places lately the advice that authors who aren't sure about electronic self-publishing can (even should, according to some) bet both ways, by self-publishing some stuff and seeking professional representation for other stuff. I'm thinking about self-publishing some spec fic under a pseudonym, and continuing to seek an agent for other works in a different genre under my own name. My question is, if I acknowledge the pseudonym openly (wishing more to use it for branding purposes, not to pretend that a subset of my work isn't really mine), does this self-publishing turn off (specifically Australian) agents and publishers as it once might have, given that a) self-published books seem to be more accepted by many readers than they used to be, and b) I would be seeking representation for a different type of work, written for sale under a different brand?
I'm curious also about the idea that large sales of self-published ebooks would (at some fuzzy value of 'large') become an advantage in seeking representation and publication (for, let's say, other as-yet-unpublished works) in spite of any remaining self-pub stigma, since it would imply a platform and a potential financial win for a conventional paper publisher. Do you have any thoughts about what kinds of values of 'large' an author would need to be in possession of for this to be the case? If an author could claim to have sold, say, 2000 mainstream fiction ebooks, would that make you think they were a commercial proposition? Or would you only start to notice if it were more like 20,000, or more than that? Or is there still some quality-driven (or snobbery-driven, even) stigma that overrules the idea completely? I think these are questions requiring new answers, now that it's clear that self-publishers are not limited in the number of copies they can physically distribute and sell. I've seen a lot of opinions on this from leading self-published authors, but not so much explicitly from publishers or agents.
I guess I'm asking whether you think there has been much change in the risk of shutting yourself out of the publishing industry by going down the self-publishing route, especially in light of new attitudes (at least on the part of some authors and readers) to self-published ebooks and this currently-fashionable advice about having a bet both ways.
I've read your question a few times and it's still slightly doing my head in. And that's because you're basically asking me to predict how publishing will 'end up' overall. And that topic makes my head hurt because it's just everywhere, all around, at the moment and I often feel like I can't get my actual agenty work done because I have to spend all this time thinking about change and how to manage change and how it may affect authors and publishers - and agents.
I've already written some posts about what's changing in publishing and my potentially crackpot theories about what may happen - they're here if you're interested - so I've possibly already addressed some of what you want to know.
Generally speaking, though, I have this to say: we don't know what is going to happen. I can't, with any certainty or real authority, tell you that this or that is going to happen and, thus, what you should do. What is going on now is unprecedented since the printing press was invented because, well, we're dealing with the invention of a new type of printing press. So I can only offer more crackpot theories. Pay attention to them at your peril.
First I'm going to address the question about what will constitute 'large' sales. Currently sales figures have to be taken in the context of their territory - the figures that make a bestseller in Australia barely raise an eyebrow in the US, for example. That is probably about to change in the English-language market in relation to certain types of books. There will be a day, probably not too far off, when I believe certain types of genre fiction by certain authors - even those published by large multinational publishers - will be published as digital only. At that time the worldwide rights holder will probably not think there is much reason to sell rights to other English-language territories when they could release the English-language ebook into world territory all at once. That way they get to keep all the royalties and they don't have to worry about getting files to other publishers, etc. If that happens, how, then, do we measure 'large' sales? If there is only one territory, what is the benchmark for a bestseller? These are questions I cannot yet answer. And accordingly I can't answer your question because it depends on what's going to happen in future.
Now let's look at the self-publishing 'stigma' - true, it's not what it once was - for certain types of books. Again, what's changing in publishing is probably going to change at different times in different ways depending on the types of stories and content involved. If you are self-publishing a children's picture book at this point in time, you'll probably still find there's resistance to that; if you are self-publishing an urban fantasy ebook, not so much.
So now to your question about whether or not you should self-publish some material and not others - I've written before about how authors can think about categorising their content. If we combine that with what was said in the paragraph above, there is certainly an argument for self-publishing some types of stories and not others. Will this prevent you from getting an agent or publisher for the 'others'? I really don't know. Publishers and agents may decide that protecting their brands is more important than anything and, thus, anyone who has published other stories/content that don't fit with their brands isn't welcome. Maybe that's how they'll sort through the increasingly large amount of submissions that we'll all see. But that's a hypothesis.
Something else to consider: if you are writing enough material that you can publish in two or more streams - and keep up the pace - I'd say go for it. But that's a lot of writing. At this point in time, when authors are actually in a very good position to start making decisions about how, when and where they're to be published, I'd advise a bit of patience. Keep writing, stockpile some stories and see what happens over the next few months. And it's probably only a few months we're talking about. The pace of change that's happening now is such that everything is going to look different for certain types of books within the next year or two.
And if you really want to keep track of what's going on, as it happens, I cannot recommend The Shatzkin Files highly enough.