I find it amusing the promo shot shows it running on an Apple Thunderbolt display - which famously does not support HDMI input, only Thunderbolt - for which there is no MHL adapter.
Yes, you could use some HDMI to DisplayPort adapter and in theory the thunderbolt display should support that, but you'd lose the webcam, ethernet, firewire, USB, microphone, speakers and daisy chaining support as DP does not support the data pipeline.