Here's a bit of info that's likely better written than anything I could type here.

Basically, right now you can get Serperior through the Mystery Gift option in Omega Ruby/Alpha Sapphire. You need to use the "Get With Code" option and input a code to get it. For Serperior, that code is POKEMON497

Starting January 29, you can get Emboar's code through the above linked website. Samurott will be available in February for those that sign up for the Pokemon Newsletter before January 31, though I'm sure the code will be the same for everyone, but it's probably better to be safe than sorry.

These codes will be available for you to use in-game until November 15, 2015.

I did get a Serperior and breed one with it's Hidden Ability. Probably gonna do the same when Emboar is out.

You can now get Emboar. His code is POKEMON500

More than likely, Samurott's code will be POKEMON 503 when it becomes available.

Samurott is up. Code is POKEMON503.