The man had a drug problem. Everyone in the Entertainment Industry knew he had a drug problem.
So does he avoid dieing in 1982 but continues his roller coaster ride with heroin, coke, et al? Some probability he dies at a later date. Good chance he has an up and down sort of career based on combinations of: a) his need to get work for money (for drugs), b) his ability to identify good scripts/parts, c) his ability to stay somewhat sober during filming, d) the quality of scripts/parts sent his way, e) his ability over time as he continues drug use to maintain his comedic talent at some sort of level of quality, and f) the willingness of the guys with the $$$$ to risk a production that depends in large or small parts on having a functioning Belushi on set.
Maybe I'm being too harsh on how hard core drug usage might reduce his ability to perform comedically. Lots of long term sucessful actors and comedians who are/were alcoholics and dabbled (or more) in coke.
I can't think off the top of my head of any shooting star actors who started out brilliantly, but burned out fairly quickly do to drug use without dieing. I'm sure there must be. (Child actors need not apply to this question)
A mostly sober Belushi probably has a career path resembling in quality some combination of his SNL companions: Chevy Chase (highs and lows), Dan Ackroyd (very solid, but needs an ensemble), and Bill Murray (mostly highs).