I think you mean 10.5.8. 10.8 isn't out yet. As for CS6, not being out yet, we can't comment on whether something is worth it. While betas are still out there, they are subject to feedback from their testers. If you want a beta when it is finalized to become available for older operating systems or older machines, contact the vendor of that beta and say so in their feedback page.
https://discussions.apple.com/docs/DOC-2455 will tell you if it is worth your while to upgrade to Snow Leopard.
https://discussions.apple.com/docs/DOC-2465 will tell you if it is worth your while to upgrade to Lion.
For Apple product feedback post to http://www.apple.com/feedback/ For Adobe feedback, post to https://www.adobe.com/cfusion/mmform/index.cfm?name=wishform