XC will lose money, but perhaps not as much as you would think. It depends on what they can run - clearly they will cancel the least profitable services first, insofar as they are able (they can't just run peak trains, for instance!). It's not a hugely profitable railway; VTWC would suffer more.So essentially only concequence of the RMT's action is to cause major anguish for thousands of passengers, increase public support for DOO, and make a very hard day for the person opperating the XC twitter feed!
Could Arriva's bid for the franchise renewal in 2019 be effected?
The only way that any future bid might be affected would be that DfT's evaluators are likely to scrutinise any plans that have the possibility for industrial action and possibly risk adjust the bid if they deem that Arriva are being over optimistic, given their past performance.