I'd thought that maybe I could get away with median because there'd be enough who are out of the league (or not going to get meaningful starts), but it's just not doable.  Right now the median is Josh Allen with 49 games started.  That will definitely increase.

That said, right now, of the 30 first round QBs drafted in that decade, we can (barring something crazy) rule out meaningful increases in games started for quite a few, so we're looking for the #15 guy in games started among those 30, which seems likely to be in the range of Blake Bortles (73) or Sam Bradford (83).

QB's who will almost end up with more than 83+ starts include

1. Cam Newton (139*)
2. Ryan Tannehill (121*)
3. Andrew Luck (86)
4. Sam Bradford (83)
5. Jared Goff (76*)
6. Carson Wentz (75*)
7. Jameis Winston (75*)
8. Patrick Mahomes (53*)
9. Baker Mayfield (51*)
10. Josh Allen (49*)
11. Lamar Jackson (44*)
12. Kyler Murray (39*)

QBs will who will almost certainly end up with less than 61 starts

1. Paxton Lynch (4)
2. Johnny Manziel (8)
3. Dwayne Haskins (13*)
4. Tim Tebow (16)
5. Josh Rosen (16*)
6. EJ Manuel (18)
7. Jake Locker (23)
8. Brandon Weeden (25)
9. Christian Ponder (36)
10. RGIII (42*)
11. Blaine Gabbert (48)
12. Mitch Trubisky (50*)

Among the options we have left, we're basically looking for the median of this list

1. Blake Bortles (73)
2. Marcus Mariota (61*)
3. Teddy Bridgewater (56*)
4. DeShaun Watson (53*)
5. Sam Darnold (44*)
6. Daniel Jones (33*)

I'd comfortably guess that at least Bridgewater and Watson pass Mariota (Darnold could as well, the option for next season has already been exercised and Jones is a bit of a wild card) so that puts 61 as the floor (and actually a bit higher since Mariota probably gets a few starts more).

Best case scenario, 3 of them on this list go over 83, and then the median would be 78 (Bortles/Bradford representing the median)

So while we can't say with certainty, it's a pretty safe estimate that the median for that decade will be somewhere between 61 and 78.  Big question is how you feel about whether Watson gets more opportunities and what Daniel Jones turns into.