I hope nobody is really expecting Van Gaal to announce that he's leaving today, or expecting some sort of announcement from the club. Even if he was going, it wouldn't be announced right as he wins the cup, or immediately upon losing it.
There has been a lot of paper talk because it's the last game, but I reckon that the absolute best case scenario is that, IF we were to lose, the club might start to think about replacing him (I still think he'd stay) and, if they did eventually do so, it'd be in a few weeks when they've had plenty of time to dither around and there's no time for the new manager to get players in....I'm so optimistic but I'm genuinely expecting this sort of thing with the way we're run now.
That, or no announcement will ever come and the season will start with Van Gaal smugly saying he told us he'd see us next season...