Does anybody know if GOG will bring Linux support to Icewind Dale II?

GOG just sells games, they have neither the developer resources nor the IP rights to port win32 games to Linux.

There's a slim (but non-zero) chance that Beamdog may create an enhanced edition for IWD2 like they already did with:

Baldur's Gate: Enhanced Edition
Baldur's Gate II: Enhanced Edition
Icewind Dale: Enhanced Edition

The reasons why the chance of this happening is not very high though, are explained here: http://www.pcgamer.com/nightmares-abound-for-icewind-dale-ii-enhanced-edition-beamdog-boss-says/

But if it does happen, they'll almost certainly make it cross platform like they did with the other enhanced editions, and GOG will then probably distribute all three versions (Windows/Mac/Linux).

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In the meantime, you can play the win32 version of the game on Linux, using Wine.

That's what I did, and it worked well. Only issue I found was that alt-tabbing to and from it could cause the screen resolution to get messed up which was annoying (but not a big problem).

There's also GemRB, an open-source cross-platform re-implementation of the Infinity Engine made by fans - however it is still too incomplete. Baldur's Gate allegedly already works decently with it, but IWD2 not yet.

If you want to give a try to Icewind Dale II on Linux but don’t want to learn how to use and configure WINE, I have a solution for you:
Install the Icewind Dale saga on Debian/Ubuntu/Mint/etc.