Kojima is finally free. He will never work on another MGS again, both because he is not interested and because he wouldn't sacrifice his dignity.
That said, I think MGS can survive (lol) without Kojima because I think there is enough material to just build on top. Remakes would be a good approach. I think MG+MG2+MGS can be put into a single game (I feel they are too short individually to warrant a separate release) and some of the lore can be re-written to match what happens later more smoothly.
MGS2 and MGS3 would be amazing in a remake format.
MGS4 could even make it with a remaster.
In a world where Shenmue III exists, I think there is a really good chance there will be remakes and new entries in the saga. Not really interested in new entries unless they are some sort of anthologies where known characters perform smaller missions.