Pardon the snarky reply, but from a professional editing point of view, one NEVER updates a working machine, unless something is offered in the new OS that one needs right then and there. And when one does update, one needs to do a boatload of research first, to make sure that every application they rely on is compatible with the new OS. Because if it isn't, it means the edit station cannot function properly, and that means that one cannot work and make money with that station. So ALWAYS look, and look well, before you leap.
You want to make use of iCloud, when it is "finally rolled out." OK, why not wait to update the OS until it is rolled out? You don't need it now, you need it when a feature comes available. SO use what you have until it comes, and then research to make sure things work. And if you really need iCloud, can you not just get another computer with Lion to access all of that? So that your current system can run under the OS that it works well? And yes, Studio 2 might have worked under all those previous OSes, but support for the old software will stop at some point, because Apple looks back only so far. So this might be the point where it doesn't work.
But really, FCP 6 and LION might be an issue. I do know that the INSTALLER for FCS2 is PowerPC based, and requires Rosetta, and Rosetta isn't included in Lion. Lion not working with Apple's own software? Well, yes, it does, the NEWER ones. The older software? As I said, they extend support only so far...they can't keep looking back if they want to look forward. If you want things to always work with the latest OS, then you need newer software. You cannot expect the older software do always just work...it won't.
Especially since FCP X is out...Apple doesn't give a hoot about supporting the older versions.