I hit level 30 and did not get the achievement. I think I used the console command and forgot to exit and re-enter the game. I am wondering if once I get some DLC and hit level 31 will it possibly give me the achievement?

YOU CAN'T USE CONSOLE COMMANDS OR YOU WON'T GET THE ACHIEVEMENT.

I KNOW THAT BUTTER! Oh wait I know how to turn caps lock off. Using a console command 1 time does not permanently disable achievements. Once you exit to desktop and re-enter the game you can get achievements again unless you use the console command during that session. So again back to my question which is the following. If I were to get any of the DLCs which raise the level cap would I get the "Boss" achievement when I hit level 31 since I don't already have it and you can't hit 31 unless you have hit 30?

There are many people I know that used the console command and did something that should have given them an achievement such as modded 20 weapons. They had already saved when they realized what they did. So they exited to desktop and re-entered. As soon as they modded another weapon they got the achievement. Just because they used the console command once it did not prevent them from getting anymore achievements ever!

It's slow, not butter.

Get it right.

And to be honest I have no clue why I used caps lock.

And no, if you're level 31 you wouldn't get the level 30 achievement.