Personally, I plan on writing my own textbook. I'll attempt to avoid the trap of throwing everything in and just focus on what is pedagogically important. I can always toss in the kitchen sink on the web so it'll be available to those teachers who want it. Anyway, I've just launched a project at Kickstarter to fund my idea. I'll spend this summer writing it and working with folks to get it into publishable shape.
My current plan is to distribute my text in some sort of electronic format and have print versions available though a print-on-demand service. So, I won't really need money for maintaing stock or delivering books. What then do I need money for? I'll need to hire an editor, pay for artwork, pay someone to do design and layout, and have some copies to give away to reviewers and such. If I make my project goal I should have just enough to get all that done, I hope. Ideally I'll hire people I already work with to do a lot of the work. Most schools have an over educated workforce, why not tap into the expertise all around me. Maybe this could be the beginning of a model where teachers are paid what they're worth by monetizing their own ideas?
How come I'm not approaching a publisher with my proposal? There are multiple reasons, but the main one is that I want to own what I create. I want to be able to post pieces (or maybe all of it) on my website for free without having to get permission. Anyway, if any of this interests you please check out my Kickstarter project.