I agree... don't buy scalped PS5. Don't support their terrible practices.
If you are able to find a legitimate PS5, pull the trigger. Following some of the Twitter accounts that specifically watch for PS5 drops helps TREMENDOUSLY! That's how I was able to get my PS5 two weeks ago (Playstation Direct).
My opinion of buying the PS5 now, vs waiting a year or three.... in a year or three (especially with the high demand and limited production/availability of next gen hardware parts) the PS5 will still probably be 399/499. Consoles really only get price drops when sales start to decline (in order to rejuvenate cash flow).
I got my PS5 specifically to play MLBTS21. BUT as mentioned previously, I can play all my PS4 games as well, with smoother performance and increased visual fidelity (so it's a win/win). I can't really think of a reason to wait.
In fact, there is much speculation going around the interwebs that finding and buying a next gen console will actually get much harder as this year goes on, and it may not improve until 2022. Reasoning behind this is that the various chip manufacturer's are stretched thin with their production. These chip manufacturer's have to choose who to build hardware for and smartphones represent a much larger (and profitable) slice of the money pie versus game consoles (which represent a fraction of total market share when compared to smartphones).
TLDR: if you have the money, buy a PS5 when you can.