Apple's computers don't really go "obsolete" like smart phones and other products like that do...case in point, we have a 2011 Macbook Pro that my wife just sold to her sister. It was a back up with an i5 processor and 4GB of RAM. We upgraded it with an SSD and the thing literally feels as fast as my 2012 that I have all spec'ed up (for general usage purposes that is). I'd use that 2011 model all day long for normal, every day usage and it'd be perfect for it.
I have a 2012 model non-retina display. This is the model I have ended up with after owning a 2011 i7 and 2013 retina model. The retina model just wasn't for me, because I prefer to have the ability to go crazy with the internal if I want to. My 2012 has 16GB of RAM, dual boot HDD and SSD (running the OS off the SSD) and besides having a lesser screen, this machine is as fast or faster than the retina model I sold to buy and build it. I don't like feeling trapped, so for the time being, this computer is my work horse, and it does it without as much as a hiccup.
With $2,000...you are in a decent place for options. If I were you, I'd build a 2012 non-retina model completely top spec'ed with the high end i7 and I'd spend the excess money you'd have on a decent sized SSD and 1TB HDD dual boot. That's just me though.
If you must have the retina model, definitely have at LEAST 8GB of RAM. That will quickly become the standard. Storage is kind of a personal preference...you can always do external, but I like having internal storage for my personal stuff...maybe I'm just stuck in the older generation, but I haven't really bought into cloud storage and prefer internal to external.
Future proofing something like computers is kind of an endless effort, but with $2,000, you should be able to get a very nice machine over several spectrums and options.