Getting ahead of myself here. I believe the chances of the Knicks winning games 5 and 6, while unlikely, are decent at maybe 1 in 4; nothing to write home about but there is hope.
But despite the issues we've clearly seen, from Randle's brain freezes and Obi and IQ's deer-in-headlights playoff performance to RJ's inconsistencies and Mitch's lack of versatility, I'd keep this team together, again on the 1-in-3 chance that a) RJ becomes a more consistent regular season player and then elevates a couple of levels in the next playoffs b) dependency on Randle is reduced, because JB's control of the team becomes more entrenched and c) Toppin and Quickley realize that success in the regular season does not translate into playoff strength.
This leaves the problem with Mitch. I think he's years away from being Camby 2.0, which means we either develop Sims (does he even have any jumpshot) or look for a backup 6-10+ big with more offensive skills. That would be my acquisition priority with any chips we have for next year.