The major issue is the stock that nobody seems to want to do anything about.
As pointed out in the thread about Southern's 455s, just because nothing is in the public domain about rolling stock it doesn't mean that discussions aren't ongoing. If discussions aren't ongoing, no amount of speculation is going to make them start because a conscious decision will have been made not to consider more rolling stock.
However, neither side is going to show its hand until the contracts are signed and it would be folly to enter into those contracts without fully assessing the knock on impacts on the overall costs of the operation.
At the very least, Cross Country needs to get back to the point where it can run the old timetable with 53 Voyager diagrams first and be bringing in the same revenue before thinking about any further changes.
There does seem to be a general perception that the increase in fleet is just going to happen because the rolling stock is available. I suspect it is far more nuanced than that and the subject of negotiations involving many more parties than DfT, CrossCountry and the leasing companies (and very much not in the public domain).