What are you talking about?
I would wait for the new mm that will be released this fall as I am sure it will be chock full of novel stuff just as the new Mac Pro looks to be.
When it comes to computer stuff, I tend to think newer is better and assures me a longer useful life span than starting with something already outdated. New software is programmed to run on new hardware so at some point that old mm will not work well with that new version of (fill in software name here) that you want to try or buy.
In computer years, 4 is old and dumping money into something as disposable as a computer could be better spent IMHO