for ipad no, for android tablet (or even better, phone) I would pay full, normal price (like of a PC game)
This is unlikely to happen but I think Paradox should be looking into it. Especially because there is serious lack of complex games on the mobile market at the moment.
I travel via public transport up to 3h daily, lots of time I just can't wait to get home to launch EU, imagine being able to do it on the go ... having EU3 on my phone would be a killer deal.
Creating the game for mobile should not be that difficult, yes it has one major problem which is the engine, would require different or special (new) version of it but apart of that it should be mostly fine.
Whole game would be the same, zooming in/out if something's too small is a piece of cake, would need complete overhaul of UI but code wise, if EU does not rely on DirectX and runs on OpenGL then it should not be that difficult, at least for Android where applications doesn't have to be rewritten in Java thanks to NDK.
Phones today have at least 1GB ram, 1.5Ghz CPU with 2-4 cores, a lot of power to use if coded properly
EU is not an FPS game which really requires mouse (FPS are terrible on touchscreens no matter what other say),
if you look closely, EU is kind of simulation, mostly about pressing buttons, moving sliders, and directing units - this can be easily remade with UI designed for touchscreens,
in EU game pace can be adjusted so that is also something worrying.
I would even date to say it is nearly perfect match for mobile gaming.
Imagine possibility of joining multiplayer game anywhere you are (mobile 3G/4G network) as well if the game could be the same as on PC gameplay/mechanic wise (just different UI), playing game on the phone and continuing on PC at home would be great, but on the other hand I am afraid that bringing game to mobile would dumb it down and simplify not giving similar experience as on PC, that would throw off lot of people ....
I think Paradox maybe could toy with the idea of bringing EU(3+ ?) game to mobile after releasing EU4, there's a gap in the market for it that's aching to fill