Could you sell the games Baldur's Gate 2 and The Throne of Bhaal (the original non enhanced version) and Icewind Dale and Heart of Winter (also the original non enhanced version) in the near future?

They are included with the enhanced editions.

The very first line of the respective store page:

Baldur's Gate II: Enhanced Edition includes the classic Baldur's Gate 2 Complete.

Icewind Dale: Enhanced Edition includes the classic Icewind Dale Complete.

Unfortunately you have to buy the “enhanced” versions to get the originals now. I would wait for a big sale, spring probably, and get them for as near to nothing as possible (and avoid spear of whatever). The less money to beamdo the better. Or pick up a cheap disc copy of the net, disc image it, and get big world or tutu and play the lot in one big go in BG2 engine.