Would get modest/average sales, but I think Nintendo has stated before that they won't remake their big titles for a console that is already backwards compatible with the original. TP HD would probably be better suited for the next home system, and there are already so many Zelda remakes this gen.

I'm honestly hoping Nintendo decides to do an HD remake of Twilight Princess in 2017 and make it a launch title for their next console. If they do that, I think it'd sell quite well, assuming there is an appropriate level of hype for Nintendo's next console. Also, it would be 11 years after it's release, which is the same time between Wind Waker & Wind Waker HD (for Japan at least).

No it's not, and no they won't.

3M... No way!
It will sell like The Legend of Zelda: Wind Waker HD or even a little bit worse.

They would probably use the style from the wii u demo (wich was just TP remade) and would sell up to 3m.

This. I don't think people would buy HD versions of a game that was launch and can be played on your current console.  Better to use their efforts on new IPs or older games from GC, N64 and create an HD version or sequel to those good IPs.

Wind waker HD is already at 1.6m (with digital) and counting. It will easily end above 2m.

Vgchartz has the game at 1.29m so i was refering to that figure. Anything that WWHD sells then i'd expect TPHD to sell a little more because twilight princess is more popular than windwaker.

Better than WWHD. 2-3 million I'd guess. Partially would depend how far they went with the graphical upgrade. Twilight Princess is now the 3D Zelda game that needs it the most, since the N64 games look GREAT on 3DS, and Skyward Sword is more stylized.

a lot, that's the most mainstream zelda game after ocarina of time.