Project Thor was ultimately derailed due to the costs involved and the negative media reception involved in having Bombardier build them elsewhere. It would have been great to have an extra carriage, but it seems the sums just didn't make it a worthwhile prospect to pursue with. In theory it made good sense, and certainly would have saved a ton of fuel, and thus money. I think perhaps it was short sighted not to purusue - say the Project was finished by early 2014. We would already have had 2-3 years of significant fuel reduction, and years to come, as well as much needed extra seats. However I don't know the exact figures, and assume there was some good reasoning to prevent its happening.
The problem with the XC franchise is that it has been very stagnant - aside from the welcomed introduction of a few HST sets, and the addition of some seats, there's been no refurbishment of the Voyagers, and no other additional stock. I just hope this changes in the near future, as at the rate we're going, the TPE franchise is going to have a higher quality Intercity product than XC. However Arriva have done well with what they've got, and I just hope they'll benefit from extra stock soon.
And the worse thing is, is that I can't see it radically changing any time soon. There are no refurbishment plans as of yet for the Voyagers (yet the 170s have already been refreshed again), and no other additional stock. And the overcrowding has been an issue for up to a decade now. I can't help but think it's been slightly overlooked, and I just hope at some point it will get some of the TPE and Northern magic. However it would be nice to see it sooner rather than later; although as everything seems to be all happening at once now after a few years stagnation, you can live and hope!
Really I assume we'll have to sit pretty with what we've got until the next batch of Hitachis get ordered; or perhaps the Verve or Aventra 125mph may be given a go.