The building was always designed so that the office tower and studio block could be operated separately - however, the main studios and scene docks don't really seem suitable for use as anything other than studios. Do they intend to turn them into offices with no natural light?
ITV does already have a few offices with no windows (or just the odd skylight) so it wouldn't be a huge surprise.
I wouldn't be surprised if the props bay and This Morning studio will be demolished for a new build, it's pretty much the only part of the site that could be built up on.
Also when they say all of their London colleagues I wonder if this will include their numerous indies scattered around the city.
I'd be interested to see what they do with the tower's offices which are already pretty modern and pleasant to work in.