They've used that music a few times since the current branding was introduced, normally for the kind of slide used tonight or one of their rare cross channel promotions.
CITV just ended up with a few gaps in the schedule then. The article mentions Turtles, so they lost that for definite, and at least three other shows are owned by Nick and may well also move.
Any rebrand will await completion of the transaction, I've not seen any comment as to when that's expected. As an estimate I'd think late October / November. Ofcom will have to clear the deal and as Viacom are the purchaser the US FCC might want to examine too to check market power changes, Can't see any issues with either regulator, but it'll add time to the process.
A little earlier than I suggested in this post, glad it's done now and things can move on.
I would expect a Nick strand in the morning, or a Milkshake strand on Nick Jr., with the possibility of a Milkshake channel at some point in the future.
I imagine Viacom are planning a complete refresh of Channel 5's look and graphics, as well as for 5 USA and 5*, with possible new names/visions for those two. The C5 website certainly needs a big overhaul, and there's still all that stuff about FIVE on there with old logo's and broken links and old, incorrect information. They should probably just start again to be honest instead of trying to fix the mess it currently is.