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My thinking is the chipset would be a "stackable" ARM core and eventually about a year after launch there would be a Nintablet TV Dock which is a little like the Vita TV, it effectively would double the Nintablet chipset (so 2x the ARM cores, 2x the GPU, 2x the RAM) and that would allow you to run games on the TV in 1080P while at home.
Then you could use it at home like a console (it could interface with Wiimotes and Pro Controllers and what not).
I can see two different sizes too, but initially I think a 5.5+ inch-ish LCD is a good enough size for games and tablet apps and keeps the initial price low. Later they could introduce a 8 inch XL version if they want.
Keeping the price low is key I think. Nintendo has big problems selling anything over $200-$250 it seems like.
$199.99 for the system in 2015 and maybe $99 for the home TV dock (optional) in 2016 probably works well.
But definitely a product line that's designed to grow over time and gives Nintendo the option of becoming a home play machine too if they want it to.
