Semi related, but I think standards for pitchers to make the HOF are likely to change because the old standards are going to be tough for basically most guys who started their career in the last decade.
Amongst active pitchers, you've got the four guys who are all incredibly likely to make it (Scherzer, Verlander, Greinke, Kershaw) and then you've got Sale, Degrom and Gerrit Cole who all have a shot. Those three all 30 or older though.
Amongst guys in their 20's right now, there are only three (!) with more than 15 WAR. Aaron Nola at 24.4 (at the age of 28), German Marquez (16.2 age 26) and Robbie Ray (one amazing year has pushed him all the way to 15.5 at age 29).
In their 20's Greinke had 35 WAR, Verlander had 36 WAR, Kershaw had 58 WAR (!). Scherzer was the only one who had a a slower start with 24 WAR before 30. Barring Nola having a Scherzer like 30's which is possible, the next group of guys has not been able to accumulate numbers the same way. Don't see many of them that'll get to 30 WAR before 30 either.