I think it really depends on what you really need.
Telephoto lenses are not really good for everyday
applications (unless you shoot bird everyday haha).
I'm actually oversimplifying the usage of telephoto
lenses here. Quite obviously, the 70-200 is good for
wildlife and not just birds
, portraits, and some
even say landscapes.
My friend bought a 70-200 2.8IS last year and till
date, I think it has only seen the sun a few times
only.
If you're just looking to buy a new (better) camera
body, then I think you should hold your horses and
wait for the 7D. I've read pretty good reviews about
it.
If you're looking to buy a new lens because of a new-
found niche where a telephoto lens will fit the bill,
then I guess you should go for it! The next question
is then to decide which one of the four 70-200 lens to
get... each one has its own fan base, strengths and
weaknesses.
If you're just thinking of buying the 70-200 lens because
Canon says it's the best it's got, then you might want
to talk to people who have first hand experience using
them and/ or rent them out to try for yourself before
diving into your pockets.
Good luck!