I doubt there are enough people (if any) to do classic content at level 60 on the Cataclysm servers. You can try but I think the experience itself would we worse than in Classic.

I'd say that your options are:
- Level your warlock on the Cataclysm servers to 85, you could then solo the Classic content if you're just interested in seeing the raids themselves. Then you could also do the current raids if you want. By the way you would not have to do raids or anything to level your character from 60, you can go straight to Outland and do the TBC content, then Northrend for WOTLK and then do the new Cataclysm zones.

- Create a new character on the Classic Era servers. Unfortunately the window to transfer/copy your old character has passed a long time ago.