If the spoilers and entertainment weakly (sic) are to be believed, it seems the writers are not rewriting but just editing whole series and seasons into condensed hour movies. (taking into acount the time lost for lens flares, and oooooh aaaaaahh special effect budgets).
it is like taking the entire DS9 changling war arch and shrinking it down to shape shifters attack, federation fights back, odo makes piece wearing a tuxedo, the end. In ten minutes.
I am disappointed they just appear to have sliced and diced, again assuming the spoilers are true, it is very discouraging to pay money to see this. It is down grading it to a "whenever" on tv if ever movie. we shall see how this pans out.