Correct. Thunderbolt 2 includes support for DP 1.2[1]. And in any case, only has 20 Gbit/s of bandwidth in total, which isn't enough for 5k even without taking overhead into account.
Which makes this announcement quite strange. If this iMac doesn't support Thunderbolt 3 (or whatever standard Apple is planning), it'll never be usable as an external monitor.
IMO, it would have been more Apple-y to launch this and refreshed Mac Pros simultaneously with TB 3, allowing Mac Pros to drive two (or more) 5k displays while the rest of the PC world is still tripping over 4k. But I guess this segment isn't a priority for them any more.
The bandwidth would certainly be there, and there's precedent with monitors requiring dual HDMI to get to 60hz, but I'm not aware of the same thing being done with DisplayPort.
With DisplayPort 1.3 now released, I'd be pretty surprised if manufacturers messed around with dual DP 1.2 inputs for displays like Dell's upcoming 5k. Such things are tolerated when there is no alternative, but when it's just a matter of requiring a new video card for a tenth the price of the high end display, that's the only sensible option. This is extreme early adopter tech after all. 5k is yesterday's 4k.
And needless to say, if I'm speculating it's too messy for Dell, Apple won't touch it with a ten foot pole :)
Still, stranger things have happened. If the demand turns out to be there, the products will follow - it's certainly technically possible.
The 30" Cinema Display had 2 DVI connectors, which was nasty but necessary. So maybe Apple wouldn't be too disgusted by the thought of dual TB.
But if DP 1.3 is around the corner, and dual TB would be an ugly hack that is mutually exclusive with the new standard, I could see them steering clear from that.
In principle, Apple could do something similar again, with an adaptor for two Thunderbolt 2 connectors (from separate buses!) In practice, they'll probably just wait for Displayport 1.3, tho.
Patently false claim. The DVI standard always included dual-link, even before Apple added USB and power connections, changed the connector, and passed it off as a unique invention of theirs.
