Unless they have changed things a lot they have two Florida brochures each year, the Premier one comes out in early May for the whole of the next calendar year, I.E. May 2004, for 1/1/2005 to 31/12/2005, and then there is a new year addition that will still start on 1/1/2005 but go up to Easter the following year, i.e. April 2006. So dates for 2006 from May 2006 onwards would not come out to May 2005. WDW itself doesn't confirm its rates until about August for the following year, if booking direct.
Lastly with the dollar rate on the slide, they would have to book a lot of 'forward contracts' on the dollar to predict the sterling value that far ahead.
You can 'advance register' with Virgin and they will send you a quote when the prices are loaded onto their system, sometimes a couple weeks in advance of the brochures.