Question about Chests that require Arena Ratings of 1850 etc

So if I get my rating on 3v3 soloQ or 2v2 with someone at a rating of 1850 does that mean I can unlock every single chest from both Black Temple and Hyjal every week? Or do I need to play arena every week or something to maintain my rating, I'm new to arena so wanted to make sure I understand this correctly? thanks a ton everyone!!

I'm looking to get my rating and then I can just chill and play battlegrounds each week to get honor to buy the chests that's why asking making sure understand correctly

You can indeed unlock each chest without playing a game once you reach 1850 team and personal rating in any bracket, you must earn the rating, its not enough to join a team of that rating.