I think, if they decide to perform in Europe, the US is the next logical stop. It also works the other way around. When they perform in the US the probably would also perform in Europe. I actually doubt that Arashi would perform in small venues in Europe, because they are the definition of japanese Idols, I just don't think it would make sense for them to perform concerts in Europe or the US.
Visual Kei Bands - yes.
Gackt - obviously happening.
Ayu or Kumi - I can see it.
KAT-TUN - Doubtful.
Arashi - Don't think so....
But Tegomass were in Sweden....Jin IS touring the US. So maybe even an Arashi concert might be possible. Never say never.