Ryan Tedder said RHI is the next single at his press conference. I'm not sure how reliable he is but I remember Billboard was saying SFTTR was the final single, as unbelievable as that is.
You know, as big as she is now, and with Idol, The Voice & DWTS all running and the Billboard Awards also coming up, I think she could easily have her 4th #1 in a row on the way soon as well.