@exage03040 There are certainly people that buy new sportbikes with intentions to only use them on the track, but they are surely in the minority. Most people doing track days are starting out on whatever sport-ish bike they ride on the street, then moving to getting a dedicated track bike after getting addicted. Very few true adult novices start with racing, most do track days first then move to racing after a while. Kids are the exception, the fast ones start when they are 5 or 6, but they won't be on 600s for a while.
For racing, it depends how fast you are. If you can consistently podium in the expert class, you're maybe buying a new bike every other year as contingency only pays current + previous model years. Everybody else, it kinda depends. The R1 is the same for 2015+, the R6 basically the same from 2008+. If you don't have a shot at winning and getting paid your $500 for it, there shouldn't be any speed difference between model years. Might not even matter for the cost difference anyways.
That may all end up being irrelevant. People will still be able to race a 2020 & get paid on it next year, and maybe they are just skipping a year and working on a new 2022? A turbo doesn't make any sense, the power delivery when it spools up could be a disaster in a corner.