"We're fans of Warcraft 1, Warcraft 2, Warcraft 3, and we'd love to replay those games for sure." J. Allen Brack of Blizzard, talking about making the first three Warcraft games compatible with modern PCs. "We actually have [several guys] who are working on a side project to do something like that." [via Polygon]
There's absolutely no problem at all with Warcraft II (at least the Battle.net Edition) and III working on modern PCs.
As for the first one - it's really easy to get it up and running in DOSBox.
I went through a phase of taking old games that I have, getting them to work on modern PCs (using DOSBox or whatever was necessary) and then repacking them into new installers so that next time I went to play them I wouldn't have to go through all that effort again - I could just reinstall my custom setup and they would be ready to play. Warcraft was one of the series I did this with and I played I and II a couple of years ago - perfectly playable on Windows 7 x64.
I can't distribute my custom installers for obvious reasons, so it would be great to have official, digital download versions. But sometimes there just seems to be a big myth about older games not working on modern PCs which isn't necessarily true. It's worth learning how to use DOSBox because then you'll be able to set up any DOS-based game in a couple of minutes - and anything Win95-based or later is probably playable, except for a few exceptions that might just have some kind of conflict with modern hardware (for example, the Thief games had issues with multiple core processors but a user patch was released for that years before the GoG versions, Baldur's Gate had some kind of conflict with modern nVidia graphics cards but, again, a user patch helped with that, and I found that the installers on the original C&C and Red Alert CDs would not run in 64-bit Windows, but that was easily solved by installing them on an old laptop and copying the game files over because the games themselves still work fine).
So yeah, there's no reason why you can't take your original Warcraft I, II and III discs and play them on your modern PC right now. But some kind of official re-release would be awesome.