Update (May 28, 2012) – For latest update check here:
According to this report published in Business Standard, the formal notification about JEE will come in April. The report by T Ramaswami Comittee on JEE reforms, which proposed a single entrance test for all engineering colleges, was accepted by the IIT council [Read earlier report: ISEET to replace IIT JEE and AIEEE]. An IIT director said that lot of implementation details still have to be looked and formal notification will be announced in April.
So finally, at least, there is some information as to when the formal details of new pattern will be announced. In the meantime, just carry on with your regular preparation [check here] and keep watching this space.
Update: We have already crossed half of April, and still there is no clarity. We are following all the updates on ISEET with the following blog post - ISEET to replace IIT JEE and AIEEE.