how would a HD remake work?
the BG games are 2D so the higher the resolution the smaller the graphics on the screen, which makes going beyond 1024x768 pointless.
they'd have to re-do the entire graphics for a HD resolution (probably 1080p), and i don't see that happening from an outfit like Beamdog...
Easiest would be to keep graphics resources the same size and give you a wider view area. That's been the most popular method in other up-res 2D games.
If they have access to original art assets at higher res, it might be as simple as saving the game files at higher resolution, or re-rendering them.
They could up-sample the original 2D graphics and tweak them where needed. You'd get a softer image, but it would be easier to look at than lower resolution pixels.
Or they could recreate everything by hand, like Monkey Island SE. I hope they don't. It's easy to lose the character of the original that way. Repainting everything to the same standard as the original would need a lot of resources.