Well, much depends on who succeeds him, no?
IMS Andropov was already a major power by the late 1970s, but IDK if he was ready to make his move in 1976.
I /don't/ think this leads to a much earlier breakup of the USSR -- IMO this came OTL about as early as it could have. It was driven primarily by internal forces (nationalism, economic stagnation, the decline of Communism as an ideology) that took a good long time to mature.
That said, a different leader could lead to a very different outcome. Some of the dumber decisions of the late Brezhnev years could have been avoided. In foreign policy, the pointless confrontation over medium-range missiles, and of course the invasion of Afghanistan. (Getting rid of that probably gives the USSR another couple of years of life right there.) Internally, the rampant corruption probably can't be stopped, but it can perhaps be slowed down a bit.
It's a good POD; I wish we had more Sovietologists around to do something with it.
Doug M.