I dunno I herd they were but I also heard that Rob was dating nicky.

not that we know of. There has been so much speculation over that since they started working on Twilight. The facts that we know of right now are:

-Kristen still has a boyfriend of 5 years, Michael Angarano. (there hasn't been a public statement by her that she broke things off, so until then, they are still involved with each other, despite his absense over the past few months)
-Nikki and Rob NEVER dated.
-No one in the cast is involved with each other.

The numerous rumors about:

-Rob's Ultimatum to Kristen
-Rob and Kristen's Hot Hookup
-Rob asks Kristen to choose him over Michael
-Nikki and Michael have affair! Kristen dumps Boyfriend for Rob!

Are all fake. They complete lies. Rob and Kristen have not confirmed anything. Although there is alot of evidence that they could be doing something, they have not actually come out and told us. The evidence that they might be doing something, or getting close:

-Michael, Kristen's boyfriend, has not been seen at the New Moon set, nor did he go to Italy, or the MTV awards, even though he goes with her everywhere.
-Nikki has not been seen around since before the Italy filming.
-Kristen and Rob have been seen exiting a couple hotels early in the morning. (Although, that does not actually confirm anything)

Although the evidence is quite suspicious O_o, we can't be for sure until Rob or Kristen confirm or deny that they are involved :D

dun u guys think they will be a good couple??