You won't get Jelly Bean any sooner by waiting to purchase...
Unless you find the current OS so terrible that you couldn't handle using it, I would say to buy it. I don't envision the price dropping much in the coming months, so if you think the tablet is worth it, then grab it.
If you want to wait and see if another tablet is released that is a better value, then that is an option. However, if you are pretty set on the Tab 2 with JB, get it, use it, enjoy it. It is fine with the current configuration.