Typically reserervations open in early April, I think it was at the end of March this year. This was for the period 8/16/09 - 10/03/09. The current Oct/Nov/Dec FD promo is the first time this has been offered to the general public, most likely due to soft booking volume and the economy, and that opened for bookings in late June or early July.
The current bounceback offer for guests there now is for FD for 8/15/10 - 9/30/10. While the public promotion is not always the exact dates of the bounceback, it usually gives you some idea.
Yes, if you have a regular package booked, you can convert it as soon as the promos are released, IF the dates match the promo dates, AND if there is promo availability at your resort and room category. There is only a certain number of rooms allocated to any promo, not all resorts or room categories are open for every date. Now and then I've had a client change a resort or room category to take advantage of the better deals, but most times I can get the promo applied to exactly what they've booked.