Both the Dream and Fantasy have contracts keeping them exclusively at PC for a period of time (not sure how long but I think 6 years?)
Dream: expectations are to have it continue the 3/4/5 night itineraries (possibly sticking just to 3/4 night to accomodate land/sea cruisers once the Fantasy comes online.)
Fantasy: all speculation (and at this point no confirmation) is for Fantasy to take up the Magic's 7 night eastern and western caribbean routes when the Magic heads over to the med- or wherever it might go.
While it is possible the Magic could stay, keep in mind the logistics of a third ship in & out of PC would have to be worked out. Parking for more vehicles, days in port, etc. It could be done, though expecially with longer itineraries like southern caribbean for example. IMO however speculation is right on with Europe. They aren't building that office there for nuthin'...
There was a great thread on this while back (around when the itineraries for '11 came out) but this is pretty much the summary of it.
Lots to look forward to!!!