Wales has spent a lot of time, effort and money to build a consistent Welsh brand and a typeface family that are all intended to be used universally by the Welsh Government, including in transport. I can't imagine they would want to give any of that up or water it down, nor should they.
ScotRail too is a brand enforced by the Scottish Government, regardless of operator, and is a devolved matter. They have just established ScotRail Trains as their nationalised operator, so I can't see them changing it again for GBR.