Ideally, this is how the mobile market should have matured, but now I am afraid it is to late. Nintendo and Sony needed to make the move back when 3DS and Vita were launched. If we had Cellular cabpable 4G 3DS's and PS Vita's that could do online gaming over AT&T and Verizon this gen of handhelds would be in a whole different position.
Like you stated in the OP, having a wifi only, and a 4G + Cellular capable version of the devices would benifit both platforms. People looking for a dedicated handheld would have the gadget they want, and people looking for the best all in one mobile platform would have the device they desire. Sales of both would expand the overall userbase, and help drive development for the platform.
Personally, I would have added a 3rd platform, which would have been a pure phone, that allowed the play of 3DS/Vita games with either virtual buttons, or a DS3/Pro controller. This would have expanded the market even more by allowing people that prioritzed the portableness of a pure phone over the difficulties of a pure game device to still have access to the games and help the userbase grow.
Unfortunatly, at this point I think Android and iOS are almost impossible to compete with. Microsoft is trying to get Windows phones to compete, but even for them it has taken years, and they are still a long way off from reaching anything close to the other two.
For Nintendo to have any chance at getting a device like this to work they would have to have massive 3rd party support from not only 3rd party and indie game developers, but also the support of non gaming and productivity apps. If anyone wants to compete with iOS and Android they have to have the ability to get mobile banking apps, driving apps, email/calander apps, calculators, word processors, restrants, stores, Fitness, manuel, etc., etc., etc.
Personally, I would love for this to happen, and I hope Sony and Nintendo both have the balls. and can find the finances to achieve it. It is not something that would be easy to pull off, and as I said, it is probably already to late for them to compete. However, gaming is my most beloved form of entertainment, and I would give everything I have to see a company that cares about that first be on top. If Microsoft, Google, or Apple are ruling the world of home and mobile gaming, then I am very sad for the future of this great art, entertainment, emotional, and physical medium.
Stop hate, let others live the life they were given. Everyone has their problems, and no one should have to feel ashamed for the way they were born. Be proud of who you are, encourage others to be proud of themselves. Learn, research, absorb everything around you. Nothing is meaningless, a purpose is placed on everything no matter how you perceive it. Discover how to love, and share that love with everything that you encounter. Help make existence a beautiful thing.
Kevyn B Grams
10/03/2010
KBG29 on PSN&XBL