This movie is quickly rising in terms of my anticipation for it with this new announcement.
If this is now locked in and what better source than Singer himself, it makes you wonder is those rumors of Famke, Haley etc might just be about finding time in the shooting schedule and/or payouts to make it happen.
This news also means it's highly likely Logan will also appear. I don't see how it couldn't, especially since his solo movie takes place post Last Stand and could be seen as a prequel event to DoFP now. Maybe a post credits sequence in The Wolverine as a bridging moment?