Buying a upgrade to a good GPU to future proof doesn't really make any sense. If what you have is still working really well for you, continue to use it. When performance starts to fall off, then buy a new GPU. By that time you may be upgrading to a GTX 1170 or an RX 590, who knows when you'll run out of satisfactory performance. Especially if you're buying a new, untested GPU. There could be major flaws and bugs that cause headaches and driver issues for months, let someone else deal with that and enjoy your 280x.