The Senate is going to try him- they actually have to. McConnell is just playing hot potato with it and is waiting until Biden is in office and he's no longer Senate Majority Leader. (Which, in fairness to him, is what any Senate Majority Leader would do in his situation)
In fact, McConnell is sort of playing a strange game in general right now. His team has been leaking the stuff we've been seeing in the news about him being happy with impeachment, saying Trump committed impeachable offenses, letting people know he never plans to talk to Trump again, and straight up saying he hates Trump.
But he and his spokespeople have been saying things that question the validity of impeachment at the same time. And he's not rushing the trial when he could and presumably would if he really believes impeachment is the right thing to do.
My guess here is that McConnell is trying to have it both ways right now. He seems to be trying to give the sense that he is breaking with Trump (likely for historical record reasons) while still running interference for him to avoid a full on Republican civil war and to provide cover for his caucus to vote no in the trial.