No, they really don't. Google has been clear that, in their opinion, the Nexus One hardware doesn't support ICS. And while we all know someone will shoehorn a version of ICS on there somehow (after all, someone did it for the G1), there's plenty of evidence that Google's opinion is reasonable:
- the limited internal storage (512 MB) [ICS distributions are substantially bigger than Gingerbread ones and there were plenty of Nexus One users pinched for space on Gingerbread]
- the relatively weak GPU [less ability to support and probably less benefit from the new rendering architecture]
- no front-facing camera [i.e. no Face Unlock]
- no NFC [i.e. no Android Beam]
- ...
Feel free to complain that Google and HTC made bad choices when designing the Nexus One, if you want. In retrospect, they clearly did. But it isn't at all hard to explain why the Nexus One isn't getting ICS.