No, I wouldn't be, unless new material for this putative 3.75 were highly backwards compatible with 3.5.
One thing that the release of 4e reiterate to me very strongly, and cemented to me personally, was that new editions serve the needs of the supplier of D&D, not me as a customer of D&D. I realised that I do not have any appreciable demand for a new edition. This is especially true of a new edition like 4e, that went a number of directions from 3.5 that I didn't like. This was also true for Pathfinder, which already is, for all intents and purposes, a 3.75 which is fairly close to 3.5 in structure. I don't really have any need for either of them.
I could potentially buy a new edition if it just so happens to fix all my problems with 3.5 without introducing more problems (for me) as both Pathfinder and 4e have done. Given that WotC catering to me personally seems unlikely, like I said, this reiterated to me once again that I prefer to be a player of D&D, not a customer of D&D. I simply have no need for another edition. Ever, really.
Although, like I said also, if backwards compatibility is high, I could see myself buying cherry-picked supplements for it on topics that I'm interested in.