C) Apple Cinema Display 27" Thunderbolt
The thing to bear in mind about the ATD is that it is
only good for use with Thunderbolt-enabled Macs. You can't plug it into a PC, or a games console, or hook up a blu-ray player. So far, only Apple makes Thunderbolt-equipped computers and there's no guarantee that even Apple will be making new computers that support the ATD in 5 years' time.
A third party display which offers a range of interfaces would be more future-proof, but remember that 2560x1440 screens need the more expensive dual-link DVI adapter (not the regular one) or a mini-to-regular DisplayPort cable (and there are some problems with cheap versions of the latter) so it might be worth buying from a Mac dealer.
However - I think you're asking for the impossible: in 5 years time there will be shiny new technologies and interfaces, and old interfaces may have vanished (or, the economy will have collapsed, the power will only be on for 1 hour a day and you'll have used the glass off the front of your monitor to make a windscreen for your Mad Max-mobile).
In particular, everybody is talking about "retina" displays at the moment, and it looks as if we're on the verge of a push to higher display resolutions (display resolutions have been static for some years now, as TVs and mobile devices caught up with computer monitors). Currently, the 27" Apple Cinema Display only has 20% more pixels than the iPad...
Personally, I'd wait until the 2012 Macs launch because if "retina" iMacs appear then, even if you don't want one, third-party "retina" monitors will be sure to follow.