I don't consider them one-hit wonders at all... as both "Apologize" (despite being the Timbaland remix that charted, it's their song too, and I always heard it credited as "Timbaland presents OneRepublic") and "Stop & Stare" were huge hits.
I think they will get another hit from their next album, so despite the flops of "Say (All I Need)" (a very undeserving flop) and "Mercy", I think they'll be back. The hit machine of Ryan Tedder will surely get his own band another hit.