The Sprint documentation that has been leaked says that they want to get 2.2 out "for competitive reasons". The quick response from the Droids suggests that VZW sees this as important also. So I think the perception among carriers is that this is an important competitive advantage, at least for now. Whether this is a one-time freakish event, or whether this becomes the new normal remains to be seen.
I'm not sure how we as Android users who want the state of the art to advance can encourage this behavior, but I like it and hope it continues!