It's called [Rift and Grift]. We are expecting it to grow very quickly once the patch is released. We are also advertising it in our Power Leveling Community to get the numbers up before patch. Even though Greater Rifts are not yet implemented, it can still be used for just Rifts.
To make things easier it is also a T1-T6 Rift community. Since Rifts and Greater Rifts go hand in hand, it should be useful having both types in the one place.
It is more than likely going to take off rather quickly, it does look quiet right now (no Grifts yet) but the plan is to get it up and running so it looks more interesting to people searching around for a Grift community when patch comes out.
If you're interested, check it out [Rift and Grift] (RnG for short).