I have to agree with Rafael's answer but with one caveat.
I would say it depends on what you want to do and the environment in which you work.
If you are buying the software, for you, to run in your own business then to invest in FCP7 now, as Rafael says, is really pretty pointless. The two main non FCP options as alternatives are Avid and PP. There are loads of posts here discussing the relative merits of each.
If, however, you are a freelancer and are looking to pick up work then there
may be a point to learning FCP7. Obviously it would depend on what the edit houses/potential employers in your area are using but the likely contenders will be Avid and FCP7. Possibly not so much Adobe yet but that will likely change fairly soon if CS6 lives up to its promise.
But those still running FCP7 will likely be looking to change at some point soonish so I wouldn't buy FCP7 to learn unless I knew I could make it pay in freelance gigs in the next year or so and needed it to pick up that work.
I wouldn't totally write off FCPX - its not for me either at this stage but I am keeping an eye on it, it would be foolish to dismiss it totally.
It is a time of flux but over here many businesses are sticking with what they have and know just now, so there may be a year or 2 in the old FCP7 dog yet.
I am UK based and in my particular work environment Avid dominates totally and those that have switched from FCP have switched to Avid. However some are waiting for all the dust to settle so there is still FCP7 work out there but it is diminishing.
best wishes
Neil
http://www.patience.tv