I'd like to have a 3.75. I think there is room for a major update of 3.5 which is backwards compatible with 3.X (and even earlier editions) in a way that 4e doesn't look to be, and which isn't merely adding some errata (some of which is of questionable value) the way 3.5 largely is. I think I'd be happier with a game that fixed 3.5's problems, rather than reinvented the wheel. I know that some would rather have an all new wheel, and that's fine. It's just I'm not one of them.
I think that the biggest problem with a 3.75 though is that those that aren't happy with 4e are for the most part precisely those that are very opinionated about what they want from the game and are no more likely to well recieve a particular 3.75 revision than they are a 4.0 edition. So really, I'm in some way closer to 'wait and see' except that there is no chance at this point of me adopting 4e. Of course, realistically, even if a 3.75 was out there, realistically the chance of it being more the game that I want that 3.5 is pretty small (since 3.5 was actually less of what I wanted than 3.0 in many ways). So, even though I think there will be a lot of 'grognards' like myself that would rather play 3.X and are frustrated that 4e material is in no way compatible with our purchases of the last few years, no company can really expect any D20 variant to appeal to more than a subset of that group. If you could get the whole group behind one product, then it might be profitable. But you won't be able to do that, because different people who are mostly happy with 3.5 are annoyed by different things about it.
I think the result will be that you'll see alot of variation in homebrews out there compared to 3.X era, as the community forks again to a degree it hasn't since the 1st edition era.