Yes in essence it's true (not sure about the times scale thing though - the plan might be for everyone to take it AS year in the future, but I've been lead to believe that the new exam will be taken in December of A2 year certainly for the first few years). It's been touted for about 3 years. Most were hoping to bring it in for 2006 entry, but didn't get their acts together in time.
It has been mentioned a lot (including on many medical school websites!) - so how much warning do you want?
It's supposed to be a new test, not the BMAT (but I'm guessing BMAT schools will still use BMAT), although some schools (Barts and the London and Kings) are apparently running the MSAT exam (details on the ACER website).