It would require a different physical transport. So you will have to wait till they come out with the UHD player next year - Sony already said they won't bring one to market this year.

I was kind of disappointed that the Sony UHPH1 doesn't let you stream 4K services however. WTF is with that? The Roku 4 does it for only $30 more than the regular Roku 3. Sony couldn't throw 4K streaming in this up-tiered box?