Silly question - because a 4th film could make a shed load of money and will do nothing to diminish the pre-existing trilogy unless they really screw up and kill the surviving characters from the earlier movie in the opening scene...
Will happen when the actors don't return.
Speaking of actors... Rutger Hauer was missing in this.
If faced with the option of a reboot with different actors or a sequel with different actors, I happy with the sequel. That way I don't have to spend 45 minutes watching a slightly different take on an origin I already know. The new Spiderman movie was ok but it didn't have to be a reboot - the change of tone could easily have led from the after-effects of the black suit.