Noone really knows what future games will need, Crysis 3 though will play maxed with a 680 @ 1920 x 1080 not at a solid 60FPs you would expect in most games. But most likely yes Crysis 3 was always going to be a system killer.
No... just no.
The GTX 680 is a high-end card, but it can only max out current gen games, future games are likely to get more demanding and your GTX 680 will have a hard time keeping up (at max settings).
In 3-4 years however you'll still be able to play modern games at reasonable settings.
i will answer your question easily , just consider crysis 3 is a next gen game .
Crysis 3 is NOT next gen. Its on the ps3 and xbox360. Next gen games are games that are "made for next gen consoles". Just cause crysis 3 taxed ur gpu and looked really good with all that eye candy doesnt make it next gen.
If you've played Crysis 3 at maximum settings, and then compared it to so called "Next-Gen" games designed for PS4, you'll see that Crysis 3 looks significantly better.
Remember, the PS4 uses modified mid-range PC hardware. It's PC equivilent will be something like a FX 8120 strapped to a HD 7870.
The GTX 680 will always deliver better performance, but since the Playstation 4 will be, like current consoles, locked to 30 FPS, and the GTX 680 is not twice faster than a HD 7870, it will not deliver 60 FPS with the same graphics. (and that's before we take in console optimisations).
I am however confident that two GTX 680's will outlast the PS4, just like two 8800 GTX's still outperform the PS3.
Yes, it's good to use that game as a reference for next-gen console ports. You'll be fine at 1080p on Ultra settings with or without MSAA for a year or two, then you'll have to drop to High settings, then Medium as the years go by. But personally, I don't see any reason to keep a video card for more than 2 years - why miss out, while you can still get a little cash for your current card?