If there's one thing I've learned being in this industry, it's that you can never predict where technology will be in the future. Right now, tablets are becoming very popular, especially now that Windows, Apple, and Google are all focusing on the mobile market. In fact, the very definition of "Personal Computer" is changing.
With the popularity of taking your computer everywhere (and tablet devices), computers will become smaller and lighter over time. If you exclude professionals and certain clients, there is less and less of a need for expandable, big machines. It's a shame to lose that customizability, and I'm sure there will be manufacturers to cater to that market - But I do believe the majority of them will produce smaller and closed systems.
With the merge of the mobile and desktop OS, touch screen controls will probably become a much bigger part of the experience (just as the trackpad implemented multiple touch with the lastest MacBooks).
4G (or whatever standard of mobile network is implemented by then) will most likely be a part of the MacBook by then. Also, Wireless AC will most likely be a standard then (current MacBook Pros only have Wireless N cards installed).
Screen resolutions are becoming much larger, so the Retina has that covered. The nVidia GT 650M might struggle in a few years time though, even if it is incredibly powerful for the size of machine it's in. It struggles with certain tasks today, so it's going to be interesting to see how it handles tasks in a few years time. The camera will very likely look dated by then too.
Of course, technology is always changing, as I said before. Something radical might come to the computer market by then that requires lots of power.
So what's the verdict? Let's look at the machine today: The MacBook Pro Retina is a beautiful, light, and very fast machine by today's standards. I cannot state how much I love this machine. It's true, it might be outdated in a few years time. That doesn't mean it won't stop being good at what it does today. Plus, by the time the new computers of tomorrow are released, something new will be coming out and rendering them outdated. Purchase what you need today, for you are here today.