I'm afraid it would be pretty much the same as it is now. Much as many Elvis fans don't like to acknowledge, at the time of his death Elvis was not a very influential force anymore, certainly not with the type of music he was making then.
He was seen as a relic from the past who got stuck in a rut, and to some degree, he was.
He wasn't being ridiculed for no reason. His (mis)management had painted him into a corner and Elvis' subsequent dependence on prescription drugs to help him cope, didn't help either.
So: if you're talking about Elvis the way he was in 1977, not having died but survived then
a) he probably would have died in 1978 or at least before 1980;
b) if he wouldn't have cleaned up his act prescription drug wise, he wouldn't have been able to make a (musical) impact, but we would have continued to hear and read disturbing news about him and his health
c) even IF he'd cleaned up his act and survived, I doubt he would have rejuvenated himself musically. Why? Because maybe the sacrifice he'd have to make to get well again would have been to totally withdraw from public (showbiz) life for a long time to totally clean his body and mind.
Not quite what many Elvis fans like to dream, but this is my - another Elvis fan - realistic take on it.....
