There's no reason to be in too big a hurry, but Carolina is not starting out fast so far. They have three interviews - Marc Ross, Dave Gettleman, and what I'd consider a courtesy interview for Brandon Beane - for their open GM job, and might be waiting for the playoffs to square up with another candidate.
Maybe it's the holiday. Maybe it's not really a situation where Rivera is in limbo. But, if a decision is to be made, apparently a lot will be riding on this Saturday conversation. It appears the GM situation may be riding on whether or not Rivera is allowed to stay - if not, it still appears to be holding for it. Richardson apparently setup a similar conversation with Marty Hurney the day he was fired, though it may not have been on Hurney's knowledge that the conversation was that in depth. You might consider it an interview for a job Rivera already has.
It should likely deal with where Rivera feels like he must improve, what he feels like he'll need to fix in his staff and himself, and what direction he sees the team heading. What's unlikely is whether that interview might provide Rivera additional power, or guarantees past the year.