Firmer schedules will be available closer to the end dates for each game.

It won't shock you to hear why Blizzard is taking action: the effort involved wasn't worth it anymore. While there was still a "decent" number of people running XP and Vista when Microsoft itself ended support, that's no longer the case. The "vast majority" of players have moved on to newer Windows releases, Blizzard says. As Ars Technica points out, the move may well be linked to the internet connection requirement for these titles.

The odds are that you won't be affected if you're reading this. However, this will certainly matter for people holding on to a borderline PC that can't upgrade to Windows 7 or later. It's a particular problem for gaming cafes in China and other countries, since they tend to hang on to older operating systems and don't always have the money to replace their PCs. There will be people who'll notice, in other words... the fallout just won't be as severe as it would have been a few years ago.