I feel like Crysis 3 is built with having upward mobility in mind. Maybe down the line the devs will release a DX12 or DX13 patch, when the time comes. Notice how there isn't any Ultra settings for graphics yet?
That being said, Crysis 1 was made 6 years ago and still to this day looks better than many of the current releases. I expect Crysis 3 is going to do the same.
Got any extra Titans you could send my way? lol
I think DX12 and DX13 will be a long time away - and with Windows 8 carrying 11.1 support, the slow adoption of that will hinder a potential DX12+ uptake for games even more.
I agree it's a very scalable engine though, and if there are expansions to the SP (or DLC) we may see it pushed even harder on the technical front.
As for spare Titans, they'll probably end up going to my Eve Online corp, where all my old graphics cards end up

Handing out old hardware is like finding a good home for a puppy.