I vote for Cougar since it just sounds right and has a familarity to Jaguar which everyone is accustomed to. Its definitely gonna be 10.6, I just can feel it right now.
Lynx is definitely gonna be a future version of the Mac OS, since Apple patented both names (Cougar) sometime back I believe.
I still find it hard to believe they will continue the decimal points up to 10.9 or further. Like I said in a post earlier, with Mac OS 11.0 Lynx might be used as a marketing piece to signify a link to the past and link to the next generation of operating systems from Apple. Then with 11.1 they start a new set of codenames not relating to cats. Its possible they might not even use codenames in the next generation marketing for Mac OS anymore.
Somehow, I suspect they might use names of special places like Microsoft is doing: Fiji, Vienna.
e.g. 11.1 - Negril (a beautiful place in Jamaica near the beaches)
11.2 - Maui
11.3 - Morocco