If you want to buy Office, do so _now_. You will of course get
11(sometimes called 2003), which is a must-have in my opinion. Usually
MS offers a discount for those who upgrade from one version to the
next, so your money won't be completely wasted. And the months of use
you get from 11 will be well worth it.
Then again, I can't guarantee MS will give you an upgrade-discount.
If you want to hold off for a while, just get the freebee:
http://www.openoffice.org/
And you don't want 12 beta pre-release now anyway. It's months away
from being a finished product (if such a thing is possible). Right now,
it's so buggy (so I've heard), nobody but an experienced user
should attempt it.