Cobain allegedly wasn't comfortable with fame. I feel he was more uncomfortable with intrusion into personal life issues. How he'd cope with twitter etc, who knows.
He was a drug user too, & that could've impacted on the bands trajectory.
However he was also quite innovative in his stuff.
b3h Nirvana & the "seattle scene" was an underground thing that took off ridiculously. It's an area full of contradictions, as the bands associated were spiralled to fame via MTV etc, despite being quite anti-corporate (see also pearl jam v ticketmaster). Bleach was quite low key, though there were people murmuring that there was a lot of potential there. Teen Spirit blew the scene up, but Nirvana had songs equally as strong, so were never going to be one hit wonders.
Where would they have gone? Dunno. They could've been immense - KC had a fairly good vision for where he wanted to go, as well as a healthy dose of cynicism. At the same time, he could've gone like Syd Barrett. Novoselic always had his politics, & as mentioned who knows to what extent Grohl would've stayed (perhaps KC's death thrust him on to do what he's done? Without that, he may not have gone down the road he has.) Alternately, they could've fallen apart. The worse case scenario is they could've become parodies of themselves.
There's a decent progression with their albums. Bleach is very raw (still love school), Nevermind added polish, In Utero is quite abrasive & a bit of a reaction to Nevermind. Incesticide is a good collection of stuff too.
I had a ticket for the villa arena show due for may 1994...