Can the current iMac models support external 5K displays?

[ENVY16]

I'm hoping to upgrade my iMac model later this year (Mid-2010 model, getting pretty old!) and as my current workspace is made up of a 27" iMac and Cinema Display, I would like a new 5K iMac to be able to support a 5K external monitor. Whilst we wait for Apple to eventually release their 5K Thunderbolt display, I could live with using the Cinema Display I already own as an external monitor with the 5K iMac.

My concern however is if I were to purchase one of the current 5K iMac models, would it be able to support a 5K Thunderbolt display if and when it eventually releases? If not, I'll strongly consider holding back until a new set of iMacs emerge with that capability.

 

[Sirmausalot]

Yes. You need to use both Thunderbolt ports for 5K support, 1 port for an external 4k display

 

[theluggage]

My concern however is if I were to purchase one of the current 5K iMac models, would it be able to support a 5K Thunderbolt display if and when it eventually releases?

I believe (as Sirmausalot says) the Dell 5k display will run using dual DisplayPort cables plugged into both Thunderbolt ports (using them in legacy DisplayPort mode) - but that will leave you with no other Thunderbolt peripherals at all. Currently, that's the only other 5k display in town and it costs more than the iMac itself!

The current iMac will probably never drive a 5k Thunderbolt display.
5k support over a single Thunderbolt cable will need Thunderbolt 3.
Its far from certain that Apple will release a 5k display at all, if they do they'll probably wait until they've rolled out TB3 across the Mac range.

The huge problem with Thunderbolt 3 and 5k is that (according to the announcements so far) it doesn't support DisplayPort 1.3 - which is what you need to drive 5k using a single DisplayPort connection. TB3 kludges it by squeezing two DP1.2 connections down a single Thunderbolt 3 cable - but that means the display needs an (expensive) Thunderbolt controller. If Apple stay wedded to Thunderbolt then they'll probably go that way, but I strongly suspect that other display manufacturers will go with DisplayPort 1.3 and/or DisplayPort, which will be easy for desktop PC users who can just upgrade their graphics cards to support it.

I think there's a can of worms brewing up over TB3 (which uses the USB-C connector but doesn't support DP1.3 and can only push 5k to another TB3 device) and "regular" USB-C (which claims to support DP1.3 and will be able to use it to push 5k to a DP1.3 device with just a cable adapter).

If you've got your heart set on running an external 5k, I'd wait another year. Or enjoy the built-in 5k display now and slum it with an mere 4k external.