We have recently learned that MR1 work will also happen on mobile, for both Android and iOS. This is similar to the desktop UI redesign that Flod has been communicating about regularly.
I am currently working closely with UX to understand which terms are going to change, and how this work impacts l10n. After a first analysis, the amount of string rework for MR1 should be very little compared to desktop, and will mostly affect Firefox for iOS. I will be able to give more details after Easter (since most people are off right now).
Firefox for Android strings should have started landing and will land until April 15th. You will then have until April 20th to complete and test the remaining work.
Firefox for iOS strings should land all in one bulk on April 8th, and you will have until April 29th to complete and test your work.
Stay tuned for more information coming up soon!