I would of course expect multitasking from such a device, so, say the phone rings in the middle of a game, you could answer the phone and talk on the phone, hands free (speaker phone style) whilst you are still using the tablet.
I'm not saying everyone would love the idea, but there is some merit in it.
As opposed to having two devices you have to keep in sync, two lots of apps, two set of data etc etc.
I could see some people thinking it was a good idea.
Maybe. Especially the part about not having to have duplicated apps and data. Might be at serious risk of becoming obsolete if cloud storage and fast mobile connections with large data allowances become the norm though. Even so, it could serve as a stop gap at least.