Probably we'll see new stages soon but that Group B mod is unfortunately postponed. eddy3spain (one of the "RBR mod gods") said that because it's just not possible to make realistic enough GrB physics (RBR forces active differentials and RWD wouldn't be proper). Though this doesn't surprise me because it has been pretty clear for a long time that accurate GrB physics will be impossible or hard to make. But the mod is not dead, if it will never be released for RBR then they'll change platform to Driver's Rebublic.
http://www.bhmotorsports.com/board/viewtopic.php?p=220556
I hope they'll even release some unfinished beta stuff if it will never be released for RBR. Even that the physics would be very inaccurate I still found that long time released Lancia S4 beta (with 450 hp physics) very fun and very hard to drive, I think the main thing is that it was completely different to drive than WRC cars. And the those would be still the most accurate GrB games in any game.
http://www.bhmotorsports.com/board/viewtopic.php?p=220556
I hope they'll even release some unfinished beta stuff if it will never be released for RBR. Even that the physics would be very inaccurate I still found that long time released Lancia S4 beta (with 450 hp physics) very fun and very hard to drive, I think the main thing is that it was completely different to drive than WRC cars. And the those would be still the most accurate GrB games in any game.