China tries to be as tight-lipped as possible regarding anything on Tibet or the Tibetan people. There is no official website with travel updates and closures on Tibet. If things remain calm through the annual March closing, then things could reopen in the Tibet Autonomous Region by early April. It is impossible to say at this time as things are incredibly tense, especially in the Tibetan regions of Amdo and Kham in Qinghai and western/northern Sichuan.
The bottom line with travel in Tibet (including the Amdo and Kham areas) is to have a flexible itinerary that allows you to make changes at the last minute if the area closes to foreign travelers. Last year, western Sichuan was incredibly tense. It was closed to foreign travelers all of March and April and then again for the entire month of July. These closures were not made known in advance. The government only gave a 2 day notice in advance of these closings.
I will always keep my site updated on the closures across Tibet so checking back frequently is the best thing you can do.