Based on the precedent set by Colours, I'm assuming that collecting Red Rings will have something to do with how you earn the Chaos Emeralds and, eventually, the Super Sonics. In Colours, collecting the Red Rings unlocked the Sonic Simulator stages, which then unlocked the Chaos Emeralds - here, given the lack of Special Stages or any kind of alternative mode (at least, not that we know about), I'm guessing it'll be more direct, and that certain numbers of Red Rings will unlock the next emerald in sequence. However, what intrigues me is what Aaron Webber mentioned in the c|net video that was posted - that the Red Rings are linked to a variety of unlockable content. Could they also be something to do with unlocking the alternative musics/equippable skills?
Also, I'm hoping that the Super Sonics won't be too easily exploitable for getting a good rank in a stage. Colours did this right, in my opinion - Super Sonic was invincible and could power through the stages, but the way the scoring system works in that game meant that you still had to work as hard (if not harder, without the aid of the Wisp Powers in upping your score) to get a good rank. Hopefully they've thought through the implementation of the Super Sonics in Generations as well as they did in Colours, so that you can't just S Rank every stage by getting 50 rings and rushing through to the end.
I'm thinking it's more to do with the bonus missions as each zone you have to collect 5 red rings per Sonic which in turns could open up a separate challenge? Would fill the amount of red rings nicely and as we've seen from the videos there are some very easy to get red rings.
Under three weeks to go and the more they show the more questions we end up with. Like what's with the Mega Drive? How do we get the emeralds? What do the rd rings unlock? What's in the house? What does the skill upgrade thing mean?
Only one thing we know for sure about this game. Serious effort has been put into providing one truely worthwhile game that I hope has a lasting effect on future games.