Firstly it is not a standard in any meaningful sense but a platform that happens to be owned by the main free channels and the telcos. It's actually a bit like Android except Youview can push updates without even the manufacturers approval!
The rest of Europe has adopted HBBTV as a standard already and much of the world is adopting similar HTML based solutions if not HBBTV itself.
As it currently stands a hard disk is required and that is unlikely to be bundled into many TVs in the near future. Spinning rust is too bulky, it adds cost. Flash is too expensive still for the Youview minimum of 250MB (or is it even more than that).
For the major TV manufacturers the loss of control of the TV UI is a major issue and they are unlikely to do that unless they really have to. For the UK alone it is very unlikely. I'm surprised that some have gone the GoogleTV route to be honest but I think they were imagining it would take off like Android has. Also going the Youview route removes their potential revenues from operating their on online platforms.
So for the above reasons Youview as it currently stands will not make any impact outside the UK (and it won't actually make much inside either) and won't make a major part of any TV manufacturers line up.