There are no confirmed plans for new/cascaded stock on CrossCountry.
The public consultation questionnaire for the next franchise barely mentioned new/cascaded stock as an option. Far more emphasis was put on tweaking the network and service patterns to better match the rolling stock availability to passenger demand.
Bidders for the next franchise (from December 2019) will of course be able to say what their rolling stock plan is when the submit their bid. The Invitation to Tender from the Department for Transport is unlikely to make specific requirements for new/cascaded stock. It will probably just ask bidders how they propose to run the tendered services with current/future assets. It is up to the bidders to decide if new/cascaded stock will be part of their bid.
The trend in recent bids has been for new stock orders. There's a healthy European market for new rolling stock (Alstom, Bombardier, CAF, Hitachi Europe, Siemens, Stadler), offering modern products at competitive prices, with cheaper running costs, better reliability and excellent safety.
The continued use of HSTs for frontline express and long distance services is short-termism that just delays progress. They are getting very expensive to maintain, parts are becoming scarcer and the reliability is dropping.
HSTs have a continued use on regional services, as is happening in the GWR area and in Scotland. That's a fitting retirement for the better examples in the fleet. Lower speed and less intensive use ameliorates the problems of age.