No. Use your iPad 4. What isn't it doing now for you that you expect the iPad 5 to do? iOS 7 would bring them to the same playing field software wise and I can't see the CPU being too much more powerful. MAYBE a quad core but apps are just starting to saturate dual core so the gains would be minimal currently. The only other thing outside of the obvious design change is a ram update to 2gb which I think is a no brainer.
Unless you see the iPad as a status symbol and feel the need to upgrade every generation, stick with what you have now until it no longer does what you need to do. I happen to be blessed enough to be able to buy the latest and greatest every once and a while but I don't really want to be wasteful either so I buy the latest and use it for a couple years. Upgrades will mean more then and disappointment will also be less.
Unless you see the iPad as a status symbol and feel the need to upgrade every generation, stick with what you have now until it no longer does what you need to do. I happen to be blessed enough to be able to buy the latest and greatest every once and a while but I don't really want to be wasteful either so I buy the latest and use it for a couple years. Upgrades will mean more then and disappointment will also be less.