I made a decision about this just lately and figured I should share: I'm heading into 8x10 territory in about six months if the financial planning works out. I'm using 4x5 for the project I'm doing. Not just for the cheaper film, but also because I've learned that while I like 5x7 as a format, I end up cropping off the top to something akin to 4x5 anyway. My brain sees better in that almost-square or square format. I can do the same thing with my 35mm images, so it isn't anything new.
I'm going to work on a budget of $1000-ish for camera, holders, and probably an older wooden tripod. The 300mm Bausch & Lomb and the 14" and 18" focal lengths of the rapid rectilinear I just bought *should* work on it, so lenses won't be needed at first.
So...er...that's about it. Just thought I'd let everyone know. I'm starting my project after Christmas and it'll likely take a few months since I don't have as much time to shoot anymore and some of the stuff has to wait until spring...and until I have a place to shoot them.