Punt Road and Batman Avenue entrances will be open. I would advise parking elsewhere though - it's a nightmare to try and get out of the MCG carpark after a game. I was on my way into the city last night and got stuck in traffic on Punt Road for more than half an hour.. I wasn't even going to the match.
I'd recommend parking on Victoria Parade or at Federation Square. Each is only a 10 minute walk away and it'll be so much easier to get away post-match. If you park on Victoria Parade after 6.30pm you won't have to pay anything either.