It reminds me in a way of what happened when London Midland changed hands. There seemed to be very little in the way of any announcement - even the names of the franchise! - until a long time had passed.
WG could announce the features of the franchise that were common to both bids.
However this time the bids might have been very different, so they would not want to make an announcement until they have signed a contract.
That and wanting to have a "big reveal" when it will make the most impact.
It might also give KA time to make their key appointments and be able to fill in some of the detail from their side.
There might still be detail to be agreed with the DfT (financing, the NR Valleys split and how to deal with the "English problem" for which WG are DfT's agent).
For once, the RMT doesn't lay into foreign state ownership, and merely castigates the franchising process.
They are stuck with it now for the next 15 years, however.
I don't know what the WG were doing in agreeing to a union deal before it had even let the franchise.
Seems like the cart before the horse to me.