You have two options here (at least that I'm aware of):
1) Use the best-practice of always naming your routes and instead of action() you'll use route() - this helped me migrate an app to L5 without touching a single line of Blade.
2) Muddy your views by specifying the full namespace - you probably don't want that.
It would be nice to have some sort of automatic namespace resolution to ease the pain of migrating to L5. If there is already the option of doing so, I don't know how. If not, maybe Taylor should look into adding this functionality.