I have one e-book published, and the editor spent a lot of time making suggestions, many of which were incorporated in the final manuscript. I feel an obligation towards her, as well as gratitude for taking me on board. Sales are very small: I gather it is mainly to do with self-promotion, and I seriously don't have spare time (I often don't even have time to write, hence am very frustrated!). I also don't have much expertise in this area, and even with the internet it takes a long time to research.
The other manuscripts I have floating around out there being 'considered' by other publishers/agents are ... just floating. The e-book I consider to be their equal or better, according to one's personal taste. Would it be really rude to send it out for consideration as a print publication, on the grounds that it has been a finalist for an e-book award, despite poor sales? (If perchance it was successful, I think the e-publisher should get some of the profits, whatever they turned out to be.) I'm sorry if this sounds like a weird question, I'm just trying to think laterally, but would hate to hurt anyone professionally or personally.
There are a few issues to consider here.
First is the fact that you no longer have e-book rights to sell along with your print book rights, and this may be a dealbreaker for some publishers (even if a lot of them aren't quite sure what to do with e-book rights yet). Some, not all. Just so you know.
Second, the question of 'gratitude'. It's nice to be grateful. Some of my authors make decisions out of gratitude and I always ask them to not do this, because publishing companies aren't charities. They don't publish your book because they feel sorry for you. They publish your book because they like it and think they can make money out of it - not necessarily in that order. While it's good to not burn bridges, don't let gratitude overly colour your business decisions. So, no, it wouldn't be rude. The e-book publisher is not offering you print publication. Why should you then not seek it out separately? And the e-book publisher will make money from the e-book sales that would probably increase if you have a print publication too.
Third, e-book sales will be small for most e-book titles for a while until everyone gets the hang of digital publishing. Don't worry about it, just do your best with the time you have for promotion/marketing, learn what you can when you can and that's all you can do. Writers very rarely have the luxury of just writing. Most of them have other jobs, children, husbands or wives, other family members to care for, friends, pets and sometimes farms. You do what you can. Don't give yourself guilt when it's not necessary. That's what major religions are for.