The Prime Minister of Malaysia just retired this very year at age 95, so I'd say no. Hell, everyone seems to think Biden will be a 1 term president, but I personally think Biden will run for reelection in 2024 (if he is elected in the first place in 2020 of course)
The fact that he often speaks in his speeches of what he'll do "in my first 4 years" & "in my 1st term" would seem to imply he'll definitely be seeking a 2nd 4-year term if he's able to.
He obviously can't state he'll be a one term president in advance, that would make him look old/weak. The presidency is a very demanding job when you have a president that does more than just golf every weekend, I can't imagine Biden lasting 8 years at his age and he's said he see's himself as a bridge to the future which implies he intends to set up his young, female veep for 2024.