deGrom needs two more seasons just to get to the 10 to be eligible. If they're "peak deGrom" seasons (8-10 WAR per) then he probably gets in based on that.
If they're less dominate seasons, it'll probably take 3-4 for him to have a chance. That'll involve pitching into his late 30's...so, we'll see.
Interestingly enough...once you get past the
4 Sure Thing Active HOF Pitchers, things get...tricky.
Next on the active WAR list is Chris Sale (46.5), who's got a shot but has his own health concerns. Then it's some solid guys who are not HOF level and too old to realistically get there - Wainwright (39, 44.5) and Lester (37, 44.2). Then it's deGrom.
After that, the only active SP's with over 35 WAR are fading Price (35, 40.3) and Bumgarner (31, 38.2).
So, if not Sale and deGrom, there may be a while before there's another Hall of Fame starting pitcher, unless Strasburg or Cole REALLY have long and productive 30's.