I had the same dilemma, but garmin sales support recommended I buy City Select NA v7, and I'll qualify for free upgrade to City Navigator v8 when it comes out. This is the e-mail I saved, just in case:
"Thank you for contacting Garmin Cartography. Yes, you will be able to upgrade from City Select to City Navigator v8 as well. You could purchase either one brand new and be eligible for the one time free update to City Nav version 8. Please let me know if you have any other questions and thank you for your interest in Garmin."
