in the original thread, which I linked above, this possibility was discussed. however it would have meant tying bitcoin to a project which has a lot of uncertainty and is not the core use case. miners/stakeholders have to agree with (major) changes so it's up to them making decisions. so the devs are really very much constrained to the original design. how this will play out is not quite clear. advanced features (payment protocol) are pending for quite a while. technically the integration is easy to do. the namecoin source has very few original lines of code. it is rather a question of consensus I think. Mike Hearn discussed this here: https://medium.com/p/b64cf5912aa7 "It’s not a bad idea, but it’s not practical for our needs right now because it has no users. "