They mentioned HDMI (presumably MHL) in the article, which surprised me, since I expected it to be USB type C that they're waiting for. That would allow the monitor to act as a docking station. 11-pin MHL would also allow this, but it's uncommon and not on any current generation phones, AFAICT.
It depends how you want the hardware to work. If you want people to bring their own monitors then you need to support HDMI.
I would expect a docking station that charged the phone and had a built in USB port. Said docking station could hook up via USB-C and use a displayport mode to send the data across of course.
In either case though saying HDMI is for the best as it sends the signal of "works with your hardware" versus "works with hardware we will be releasing".
Does this actually enable running legacy desktop apps on Windows Phone? Or is this just for Universal Apps?
If it's the former (and I hope it is), non-x86 chips is probably out of the question. For me, this would be the killer feature that finally drives me away from Android and onto Windows Phone.
I'm also hopeful that eventually we'll see Hyper-V ported to mobile and be able to run alternative mobile/desktop OS's simultaneously.
I hope you're wrong; there's several great Windows 10-capable phones already out that should have the horsepower to accomplish this. It would be a shame for such a useful feature to be limited to next year's devices.
You can stick multiple arches in the same binary, much like OSX does. I think you can have ARM, PowerPC, and x86 in the same executable, each with 32-bit and 64-bit varieties.
The way I understood it, Windows 10 universal apps are truly universal; if your device runs Windows 10, it runs the app. This can be achieved as duaneb said, using the same method Apple has been using since the Intel switch 10 years ago.