All we can predict is that 5 years from now you'll be able to play new games that have hardware requirements similar to the current games (which is unlikely). It would be easier if your budget was thousands of dollars instead of being limited to US $850. It's easier to build a budget system that runs current games and upgrade when it no longer meets new games requirements.
Yea say for instance a 5 year old computer isnt going to play crysis 3 well at all or bf4 for that matter. A 2 maybe 3 year old computer can play current stuff on mid settings but 5 years is a big stretch on a small budget like you have. You WILL want product that can be overclocked in the future to help it keep up with software demands.