It doesn't necessarily have to be Mistwalker. MS owns both the Blue Dragon and Lost Odyssey IPs. Don't get me wrong, Mistwalker would be great, but if they're busy with other projects MS could just have their Japanese studio (Studio Osaka) work on one.
"Immigrants. That's all they do, you know. Just driving around, listening to raps, shooting all the jobs." - Malory Archer GT: Bessy67