Personally I'd wait to see what the next generation has to offer. In the meantime, maybe try your 12.9" iPad without a keyboard when going somewhere, maybe the experience improves if there is a chance to lighten the load. You could also consider going extremely mobile with just a smartphone and maybe an external keyboard.
IMO, if you're not happy with the 12.9 you have, sell it now! When the new models hit, it's value will decrease. If you can wait a few weeks, you can get a brand new 9.7 Pro model our get the older 9.7 Pro at a lower price.
I'd wait. Even if the current gen has everything you need, I think its smarter just to wait a few weeks and get new features and improvements for what would be the same price (excluding discounts on current models). Plus waiting a couple of weeks and getting the new one will get you a little more money when you go to sell it again eventually as its one generation newer.