According to a short announcement on Twisted Pixel Games' official website, the console developer has just finished their contributions to "an unannounced MMO" in development at Turbine. Based on the wording, it doesn't sound like this is a port of Asheron's Call, Dungeons & Dragons Online, or The Lord of the Rings Online, but I suppose you never know:
It's still hush hush, but we just finished a contract with Turbine to help them build an awesome new MMO intended for consoles. Thanks, Massively.
If you want more than that, you'll have to take it up with Turbine, because we can't spill the beans on their top-secret game.
It was a fun project, and we're proud of our work. We can't wait to play it ourselves when it's released.