Ego's at the door.. or Axel on proper medication.. they would need to simply tone down the drugs and alcohol to do that.. I am in 2 bands.. a (Hard rock style band and a modern Country Western styled band) and we have booted folks out of the band twice for being drunk at practice or a gig.. of course it wasnt always that way.. back in the day (god i sound old) it was sex drugs and rock-n-roll.. maturity is a good thing..
so i digress .. back to g-n-r
IF and thats a mighty big
IF they could hold it together i could see the different sounds creeping into there style.. but i dont see them altering to much on what they do.. as a matter of fact i could see an actual toning down of the whole grunge movement and maybe retain a bit of the FUN flavor in uhm.. clearing throat.. Hard Rock.. might even make Metallica think they don't have to alter there sound so much as load and reload and st. anger don't suck so much too.
the death of G-N-R marked a turning point in mid level hard rock..
I could rant on about this and i just might

ok i will.. 3 bands taht still try but can't reinvent themselves to be more then a nostalgia act..
Def Leppard died when they stopped being Def Leppard.. Hystaria.. marked the end for them..
Poison.. 2 album wonder
Motley Crue : oh how the mighty had fallen.. but Dr. feelgood was a great end point for them.
Van Halen: to david or not to David that is the question.. cry havoc and let loose the dogs of hagar..
KISS: outside of lick it up.. what? make up on .. make up off.. They were already close to a nostalgia act by 87 / 88
The 80's had just run there course.. kinda like the 70's a few bands made it out .. Deep Purple.. Ozzy .. the stones, Zep (could have and would have just because well. they were Led Zeppelin! but they did the right thing with johns death.) the eagles.. the were diverse enough to change and meld/mold with the times.. but bands like Forigner/Styx/Grand Funk/Bad Company/ and yes i am going to say it.. Alice Cooper... and others.. not so much.. they still tour.. but does anyone care at the concert if they stand and say .. hey got a new album out.. nope.. we say shut up and play your old stuff please. Few bands have the chance to move an entire music scene in a certain direction. with the death of the G-N-R there was a whole in the industry that was filled by the likes of Pearl Jam and Nirvana and god help us Creed.. actually with the lack of moment in the style and the rise of grunge which allot of the ladies didnt understand.. many folks abandoned ship and went for the southern rock sounding style of Country during the 90's..
(wait a couple more years and as country becomes more and more rock you will probably get the First Death Metal Country Western band

)
So back to GNR I always said that between them and Metallica either one of those 2 were the heir to Zep as Kings of the mountain.. G-N-R screwed the pooch on that and well .. Metallica needs to resurrect Cliff ..
I shut up now.. Long live ROCK!
