Yeah sure for console only players there is nothing wrong about getting a ps5 at launch and then sell it to get a pro version down the line , but here is the thing tho, it's always games that sell systems time and time again, but looking back in the ps3 and ps4 nothing was there day one in terms of games that made me buy it day one.
The ps3 released in 2006 and the game i bought the ps3 for was mgs4 and that game came out summer 2008 that's two years!!. the ps4 released in 2013 and the most anticipated game was bloodborne which came out in 2015 that's another two years, lets compare them to the ps2 which released in the end of 2000, but in 2001 a year later big titles were released for it like SH2,FF10,MGS2,GTA3,ICO,DMC,JaK and Daxter,Onimusha,GT3 to name a few, if the ps5 can do the same than it's a no brainer to get it day on or shortly after.