CharlieDeltaUK,
I can't find the official AOPA press release but the PPRuNe search function reveals the following from October 2008 :
At a special meeting of EASA, members of the FCL008 Working Group and the UK CAA called in Cologne on Tuesday to discuss the UK IMC rating, EASA agreed as a first step to “grandfather” IMC rating holders for life – which means anyone who gets the rating before EASA takes over responsibility for licensing in April 2012 will be allowed to fly safely under its provisions for as long as they live. AOPA UK, which was invited to an FCL008 meeting for the first time, welcomed the decision but will continue to press for the retention of the IMC rating in order to protect the next generation of pilots as we protect ourselves. In this, AOPA has the support of the UK CAA, which sent its Head of Licensing and Training Policy Cliff Whittaker to join its representative on FCL008, Mike Dobson. Together they made it clear that it is CAA policy to retain the IMC rating. EASA also sent some big beasts to the meeting, including Matthias Borgmeier and Eric Sivel from the Rulemaking Department. EASA’s Notice of Proposed Amendment covering instrument flying is due in January 2011, at which time the precise details of its intentions on the IMC rating will become known. Martin Robinson and Nick Wilcock attended the meeting on behalf of AOPA UK. Afterwards Robinson said: “We welcome the concession, having previously been told it was not possible to grant grandfather rights under EASA, but we will not allow it to take the steam out of the campaign to retain the IMC rating for the safety of all UK pilots present and future.”
A fuller report on the meeting will come from Nick Wilcock shortly.
So it looks like April 2012 is the ultimate date.