W.C.S. -
The movie isn't terrible but isn't anywhere near good enough to justify retconning the series, leaving people to argue over the ins and outs of what makes sense now and what retroactively does or doesn't make sense from now till eternity, and having to hear everyone whine from now till eternity that their interpretation of what is canon MUST be the correct one, with the new added 10,000 options.
This is also the M.L.S. (most likely scenario).
And now why don't we switch gears.
What is the B.C.S.
Best Case Scenario is this film plays as a definitive ending to the series that still ends the narrative somewhere that allows it to take place between Aliens and A3, IF YOU WANT IT TO but also, acts entirely as a closer, if you don't.