I know that SDL 2.0 is already relatively stable but I was just wondering if anyone knew when I could expect it to be officially complete. I have a game I'm working on using SDL 1.2 but I don't want to switch just yet until I know I can trust the stability 100%.

There's little correlation between SDL 2.0 not being "final" and not being good enough for you; you should use the new version and either discover bugs that are relevant to you (very likely to be addressed and defeated once found), or get to use new SDL 2.0 improvements as early as possible.
Finding so many unresolvable issues that you cannot use SDL 2.0 and all your testing has been in vain is a very unlikely outcome, and the cost of porting existing stress tests and selected parts of your engine from SDL 1.2 to SDL 2.0 should be modest.

There's little correlation between SDL 2.0 not being "final" and not being good enough for you; you should use the new version and either discover bugs that are relevant to you (very likely to be addressed and defeated once found), or get to use new SDL 2.0 improvements as early as possible.
Finding so many unresolvable issues that you cannot use SDL 2.0 and all your testing has been in vain is a very unlikely outcome, and the cost of porting existing stress tests and selected parts of your engine from SDL 1.2 to SDL 2.0 should be modest.

Actually I already started using it and I've run into a few problems with MP3's and fullscreening but nothing major. I just didn't want to have my game held back if SDL 2.0 was gonna take really long to finish.