Yes, but there is a difference between a Nexus android phone and the other manufacturers android phones. You'll notice I mentioned Nexus specifically.
For example, the Nexus S (which was released in 2010) got the most current 4.2 update and it doesn't cripple any software features for it either.
The Nexus S can do the same things software-wise that a brand-new Nexus 4 can do.
Also, most of those phones that are on 2.1 are there because of manufacturer choice and not because of Google's choice.