There are no standard hardware specs at this point so there's no such thing as "future proof", standard advice is that you buy your gadget for what they can do now rather than for what they may be able to do tomorrow.
By the time android 3 comes out, there would be a slew of other official tablets using it and you can choose from those. Which is probably around half a year from now.
Like I said in another thread. If you're looking for a long term device, you're six months too early.