Ed, what you are envisaging is a radio with a general purpose operating system that can run future digital mode software for decoding and encoding, by simply (!) installing the next version of the software.
It's a nice idea but the question is whether you'd want to burden your radio (which will probably last 10 to 20 years - or longer if you look at the ads for FT101s and TS520s) with an operating system and specific hardware that works today but might not be much use in 10 years. Would you, for example, buy a radio with an embedded PC running windows 98, 2000 or XP and insufficient memory or disk to support a later OS? All those versions of windows are now without support from MS.
I think computers will steadily become more powerful (a la Moore) and radios will diverge into new architectures, such as the SDR trend seen now. The KX3 is an SDR and has some digital modes built-in. But has the PSK31 inclusion been a lasting benefit? I think it is now rare to find a PSK31 station, whereas 5 years ago it was still a very effective and popular qrp mode. Icom has moved into sdr with the 7300 and 7610. Will the Japanese brands move into compact portable SDR boxes? I think it depends on the perceived market size.
In the meantime I think using separate general purpose radios like the 817 with general purpose "just fast enough" laptops or tablets will be the way to go.
And as you remarked earlier, taking the equipment into the field is one part of it - being able to view the screen comfortably is a big factor in the practicality of using screens in the field. A shelter, or one of those nice triangular tarps, makes all the difference.
73 Andrew VK1DA VK2UH