It's like saying everyone threw away their 3ds when the XL came out, to some people a bigger or better screen doesn't matter, people like you, however people like me want a better screen as I use the screen often. So the way I see it is they should release new consoles with better Wii U pad screens and offer to sell the new pads as an option or even do a trade-in program.
Nintendo could also make the second pad work like a normal remote on games that don't need a additional screen, it would just act as a pro controller.
3ds xl is diferent, you could keep both for mutiplayer porposes since lots of games like pokemon and such need 2 consoles and such for trades, the other 3ds isnt useless at all it still works by itself since it isnt tyed to anything only needs the game cartriges and alot of ppl actually sold in their old 3ds and payed afew more bucks and got a xl if they didnt want to keep both like i did.
the older gamepad would just be junk you couldnt do anything it doesnt work by itself like the 3ds so even by selling you would get really low value since its a device that doesnt work by itself and cant be added along others to increase the controllers on the wiiu.
Your hopping way too much from nintendo, turning the other gamepad on a pro controller? lol nintendo would just tell you go and buy a pro controller, there isnt any reason why the gamepad that got a patch to stream wii mode on the wiiu doesnt work like a classic controller,they just didnt want you to get a free controller. and make you use a wiimote with a classic controller atached while looking at the gamepad to play wii games if you dont want to use the tv.