I'm going to say, probably make the 2nd round and lose to NY. Which is unfortunate.
Even if Tatum is like 75-80% of himself, that'd be huge for this group and raise the ceiling a bit. But I still think NY is probably a bit more talented overall, and it could take time for Tatum to get acclimated again even if he has a month which could become a factor. I doubt he'll be playing 40+ minutes regularly even in April and May.
What kinda sucks is, it's looking likely BOS-NY will be the 2 and 3 seeds in some order, which means an inevitable 2nd round matchup together. I still think despite DET being the 1 seed, NY is probably going to be the favorite in the East given their roster + playoff experience (and guys getting healthy too). And I might lean picking the Celtics in a series with the Pistons actually. Not the Knicks though.
If we could avoid NY to the ECF somehow, I'd say we can make it. But it's not happening. DET has a 5+ game lead for the 1 seed. Or maybe CLE leaps one or both of BOS/NY for a spot in the 2-3? They've been red hot too. Then it's Boston vs. Detroit likely in the 2nd round, NY in ECF