I'll be giving this a miss when Mike leaves. Without the dynamic between Harvey and Mike, and Mike's intelligence and memory to play off, this show isn't going to be anywhere near as good as it used to be. The whole reason it works so well is because of how Mike and Harvey interact. Sure, there are often little bits with Donna and Rachel etc, but they're the two that make the show and with one gone, I just don't see it working.
It's also been getting rather stale recently anyway. I'm not surprised that Patrick J Adams has decided it is time to go. They've overdone so many plot lines that it is just getting silly now.