There is rally (at least one track shown, who knows how many total) but after both Dirt games it's probably going to be meh. I mean on one hand it will blow Dirt away in the handling department, even GT4 rally does. But in track amount, variety, and graphics it won't hold a candle.
From what I've seen of GT5 it seems like it won't really be the king of anything, but it'll instead have like a half dozen different styles of racing and be good in all of them. Honestly I was really down on GT5 for a while, but I'm definitely looking forward to it. Probably won't get all that far, but I'll bust out my Force Feedback GT4 wheel and have a good ole' time. Gonna play a lot of Forza 3 to get hyped up for it closer to release.
Afaik, these are the race types in the game so far:
-Street/Circuit
-Rally
-Nascar
-Go-Karts
-Night (I count it separate because man, the night races in Tokyo had a totally different feel in GT2 or 3 when they were added)
and weather conditions that are at least rain (with effects on handling) and sunny. Hopefully there is more and hopefully you can apply the weather to every track in the game.
Kaz said there'll be 70+ "unique" tracks total. Although I dunno if that counts reverse/weather changed/night etc... so far 17 completely unique ones have been shown.
