Too old and not well-placed to take power, since Brezhnev had shunted him aside. He'd be in his 70's and infirm, whilst the other Politburo members would mostly be in their 60's and a bit more vigorous. It's not ASB but would need a major POD to happen.
The idea of a Baltic Soviet leader is intresting, but OTL I dont think anyone from the Baltic States had any chance of gaining power. It'd have to be more of a long-term development in any realistic TL.
Well, we've already seen a Caucasian Soviet leader take power (Stalin), so what about a Central Asian based Soviet leader? For the Baltic Soviet leader to come to power, it'd take a lot of haggling on the part of the Soviet Russian part and a bit more compromise on part of the Baltic leaders.