On second thought...might this N2 be the "enterprise" version for business users?
To take this in a slightly different route and let the imagination go for a moment:
Perhaps the N2 is a Motorola based phone. Wasn't some big Motorola muckity-muck also at the launch of the N1? Could the N2 be a Motorola based product line? The N1 could be the HTC portion of the Google mobile phone sales plan, with an N2 being produced by Motorola, and any subsequent manufacturers getting the next alphanumeric designation, with each bringing something specific to the line in terms of hardware and software. The N1/HTC could be the flagship for Sense UI, N2/Motorola the development gem for MotoBlur, and eventual N3, N4, etc could be eventual test beds for Sony/Samsung/Dell/etc to offer a flagship model that showcases both their specific hardware choices mated to their take on the UI. It would make some sense in that they would all be a "Nexus", making for a nice play on the definition. The phones would both be devices used to make a connection (cellular, internet, SMS, MMS, email, Facebook, etc) as well as all having Google as their core.
Just throwing that unsupported speculation out there to chew on. For all we know, it could end up being nothing more than a N1 World Phone edition with minimal tweaks beyond CDMA and GSM support. But I like my idea better.