It costs money to change the interior and it was not specified in the franchise award. As noted upthread there isn't enough slack in the fleet to take units out of service for a heavy rebuild. I am sure that individual seat covers get replaced on a regular basis even if it is not immediately noticable because it is a like or like change.
It is not inevitable - it is subject to the DfT deciding to support it - depends quite a bit on pressure from politicians I imagine. How many made increased capacity on Cross Country a priority in their campaigns.
depends more on who is awarded the franchise I think as well (virgin coming back again???)
I wouldn't expect anything much at all to happen with only about 18 months on the current one left. The franchisee will be in "coasting" mode at the moment and not wanting to front up much in the way of additional costs.
it seems like an open goal to get a couple of ex LNER HST sets on short-ish lease for 18 months or so like EMR has just done.
no Avanti voyagers available until 2022 in any case until 80X are ready.
(XC would probably save a fortune on delay repay ..or at least payback to customers who can't board due to overcrowding....not to mention improved patronage with a better quality service)
DfT really shouldn't have a problem with it as it's current stock on the routes already.