I've never understood why WP8 seems to be such a fundamental shift from WP7. This is something Microsoft, imho, needs to confirm one way or another, asap, to prevent people from holding off/being disappointed due to the forthcoming release of WP8.
Imho, WP8 should be nothing more than a major upgrade, much in the same way as 7.5 was, and should be readily available to be rolled out to G2 devices at the very least, therefore not rendering the devices people will be purchasing over the next 6 months, obsolete overnight.
If Microsoft do decide that WP8 is only going to work on new handsets, and WP7 handsets are thus incompatible, then I know I personally, will never purchase another Windows Phone handset again, or indeed trust any future Microsoft powered mobile devices. Aside from my own personal feelings towards such a roadmap, if this happened, it would also cause mass fragmentation of the eco-system (with developers having to develop WP7 compatible apps alongside WP8 apps - thus most will probably never take advantage of the extra WP8 abilities, or of course just cease development for WP7 users altogether) and it will also kill consumer confidence and trust in both Microsoft, and Nokia (and other hardware vendors) products.
Microsoft has to be very careful here, the safe thing for them to do is to confirm the future of the G2 handsets for once and for all, as soon as possible, so we all know where we stand, and whether a Microsoft OS can be trusted to power our next mobile/cell phones.