I had a 6th gen and really enjoyed it, no complaints at all, great bike! I picked up an 8th gen summer before last and am really enjoying it, the 8th gen to me seems to have more tech and refinements, a more current day look and feel IMO. I really like that the 8th gen oem luggage doesn't require those ugly racks, even the oem trunk mount is more compact, integrated and clean, adjustable seat, heated grips, traction control, LED lights, and I like that the brakes aren't linked now. I added a heated seat and cruise control and am all set, am loving this bike!
You should keep your 07 RWB though and still buy an 8th gen, otherwise you'll always look back on why you sold the RWB. Neither of these bikes are expensive compared to other options out there, having one of each for not too much over $10k sounds like a great investment and future smiles of rides!
What about the 8th Gen do you like that makes you consider doing it?