Trout is a no-brainer. Trout's injuries have tainted a potentially legendary career. But even as is, he'll be around 500hrs and 7 top two finishes in the MVP when he retires.
Freeman won't be a first ballot guy. But I think the numbers, all-around play, and the fact that he is such a good guy will get him in.
deGrom has two cy youngs and as mentioned was Koufax esque for a 3-4 year period of time. Wins for SP have become highly devalued so his "counting" numbers will be based on a sub 1 whip which is historically incredible --just looked it up, literally 2nd best in the history of baseball--.
Greinke should get in eventually
Giancarlo will be interesting. 500hrs was always the benchmark and we'll most likely get there. He could be the first to get to that number and have a tough time getting in.
There's a few likely/no doubt other HOFs still active I think... Verlander, Scherzer, Kershaw