They gave up (Sidhe, then Wicked Witch). I'm not as sure as you are that RC was the "future" of the rugby union games, due to the lack of depth of its gameplay (no forwards play, no set in backwards games, no real kicking strategy ...). We're some who have expected that Big Ant, who did a great XIII game based on the same engine, takes back the licence, but there's absolutely no information that allows to think it could happen. Rugby 18, from Ecko, came out with some qualities (after a big and necessary patch), specially in its ruck system and its penalty kicks. It's still a very average soft, and the very humble size of this studio doesn't offer a great hope for a future "AAA" game, like we had a decade (!) before.
Anyway, the only news you can expect will come from them, probably in september (fitted to the 2018-2019 season which leads to the World Cup, that offer them better sales perspectives).