What the carriers allow to make it to their phones is not necessarily the standard android build, though. (Or is that what you meant?)
I'm speaking from a US perspective here; I understand in other parts of the world things are different.
I'm also in the US and I can see carriers removing this feature. I guess when I say standard android build I mean before the carriers mess with it. I feel pretty safe with the nexus one.
T-Mobile tacitly permits tethering already. They've left the DUN profile on their BlackBerrys for years.