GnR looks interesting, but my money's going to Avengers.
After 8 years, JJP has yet to make a game compelling enough for me to own. I had a WOZ for a while but it just doesn't shoot well IMHO and I eventually got rid of it. Hobbit, DI, Pirates and Wonka all pretty good games (well, maybe not hobbit), but price and other issues keep me away. In the meantime I've gotten a Maiden and JP2 from Stern and am enjoying the hell out of both of those games. Elwin is bringing new and refreshing ideas and his games shoot great.
GnR might finally be *the* JJP worth getting, but there's no hurry, and I don't see it affecting other games' value. Pinball market overal is too big and there's not that many GnR fans out there who want a pinball machine. Remember, this band is 35 years old </odin>