I want to make it clear the type of person I am before I mention my comment. I am very keen on details, and notice everything. I also am a very quick acting user, and don't like lag.
With that said, I think the mini is one of the least future proof products they sell right now, and I would absolutely wait for that reason. Believe it or not, iOS devices do slow down a little bit after a while with apps being installed and what not, and even hard restores don't rid the system of these slow downs. With the iPad mini's current "out-dated" specs, I would say it's worth the price for the update.
~My modest opinion~