I think you're worrying about seeing a refresh too much. Apple has mentioned Lion once publicly, and that was during the MacBook Air announcement. Since then the only piece of information we have gotten about Lion is in the beta release of the Mac App Store. I don't think we're going to see any additional news about Lion until June when it's time for WWDC, which is the only known logical timeframe that Apple would announce any news about OS X. But between now and then it's all rumor and speculation.
As far as refreshing the iMac, I think we're going to see it during the spring (mid-March to late May). It will more than likely implement Sandy Bridge. I highly doubt that Apple will update the iMac in Q4. So if you're waiting for the next update like I am, just jump in at the expected update in the spring.
I plan to just finding it hard to wait lol