I mean, “it depends”?
I’ve gotten a 2% increase in FTP after every 6 week block. If I theoretically do 6 week blocks until spring (3/21 for simplicity’s sake), that’s just short of 4 blocks of training. Given 2% every block, that puts me at an 8.69% gain over my starting FTP.
If you’re seeing similar gains during your blocks, you should be at around 295 by the spring. Add another block in (because, wow, who starts riding outside on the equinox, it’s still cold as heck out there) and you should see the magical 300.
I guess the question is, what sort of increase are you seeing after each training block?