There have been elevators in Brussel Centraal for at least a year and a half now. But they're not easy to find. There is an elevator from each platform to the intermediate level, an only one goes up to the main (exit) level (Of course this doesn't help if they are out of order... )

And there escalators going from each level up (but not down) to the intermediate level (which is sufficient if you are just switching trains).