I'm interested in the 5,1 Mac Pro with: 12 core (2 x 2,93 GHz Intel Xeon) from mid 2010. At the moment, from what I've read, the oldest Mac Pro's that Mavericks and Yosemite seem to support are the early 2008 ones and later. I'm a bit worried that if I go with a 2010 one, it soon won't be able to run the latest system anymore. A question, why is that so in the first place? I mean, what makes it that a Mac can't run a newer system anymore? The one I'm interested in is still the 3rd fastest stock Mac in the world according to 64-bit multicore benchmarks, so should I worry or not? Is it a marketing thing? Will I be able to run another 2-3 systems or so after Yosemite? Thanks!