I'm on the side of keeping the frame if you like it. Have you treated the bike to a real deal LBS "super" tune-up? That 105 groupset is pretty bulletproof. With a professional cleaning, proper lubrication and adjustment, etc you might be like new. Even if you had to replace some drivetrain components (e.g. chain, cassette, chain rings) with that generation's parts (which are still available!!) it would be minor, I expect. I don't know... I just can't see the new generation groupset impressing a non-pro rider that much.