Assuming HS2 does get built in full then it will clearly affect XC at some point, and I think some consideration aught to be made to allow trains to the south west to access HS2 at Birmingham and electrification to at least Bristol to allow classic compatible sets to run to Bristol and Cardiff or at least a connection at Curzon Street, but that clearly a very long way off any possible consideration and we don't know for sure if even all of HS2 is going to be built.
The idea of running Leeds to Birmingham services via Manchester using HS2 and NPR has legs if the Eastern leg isn't built, but HS2 and TRU I'm not sure it will really have the capacity for that, In any case I think you have to build either the Eastern leg or NPR your not going to get away with not building either, otherwise the whole of Yorkshire, the North East is going to go nuts at the competative advantage given to the West Midlands and North West.
So without trying to turn it into a HS2 debate, as far as XC rolling stock is concerned I certainly think they need to be looking at Voyager replacement within the next 10 years significantly before any likely completion of HS2. You could argue they should be looking at it now really although that would likely mean writing off Voyagers before they are life expired, but gas guzzling Voyagers running between York and Edinburgh, Birmingham and Manchester and even Basingstoke and Bournemouth is less than ideal really.