iPods are usually "renewed" near September, give or take. Expect a better processor + camera for sure. The current retina display is good, but people say that the iTouch retina display is not the same as the iPhone 4/s retina display. The difference is unnoticeable, and the "two different retina displays" thing may continue, unless the screen size changes, which is possible. The current ipod touch would play most of the apps on the App store. It only has 1 processor, so dual-core apps (GTA3) won't work. Walmart online has it for $187 (there 3 year warranty is pretty good), and if you don't mind open box Amazon Warehouse Deals has it for $160~. Look into Warehouse deals before you purchase however. I do not know what the warranty situation is.
I would listen to Blaster Man. Wait until September, possibly earlier. New itouch will coincide with New iPhone.