Matt is older now, so his voice has matured, which is not a bad thing. He can of course still hold the falsetto, but it would be weird if he still had the sound and tone he had when he was 19 or twenty. Plus he never said they were never going back to the OOS or Absolution days.
They just wanted to go back to being a three piece. Like Matt said, you can't beat drum, bass and guitar.
And did you notice the matching clothes in the video...a uniform to go with the theme of the video and song.