In all cities (except for London), players will now earn double job mastery now through Sunday, June 13th at 12:01 AM (i.e. Saturday night).
So, really, you only have about a day from now to get your double mastery. As you can see from the picture above, there will be some sort of "fight rewards" offered as part of the 2 year anniversary; we will have to wait until June 16th to see what that is all about.
Personally, if you are like me, job mastery is not stopping you in Bangkok but rather $B itself. I think most players who are almost done all the content would say the same. The cost of Bangkok chapter 7 is intense to say the least!
As some of you have mentioned in the comments, the Coming Soon section of Mafia Wars has been updated to include Mafia Wars Las Vegas:
Note the key words: "Fighting and battle take the center stage in Sin City."
After reading that I hope this is not referring to the new "Fight Club" but rather actual content that players can progress through using Stamina (bosses, fighting other players, robbing targets, etc).
If that is the case, it would make sense that Episodes 6 and 7 are so lengthy. If players use primarily stamina to progress through Las Vegas, then they will have plenty of energy to slowly chip away at Episodes 6 and 7. Players might be able to concurrently work through Las Vegas and Bangkok at the same time, spending stamina in Las Vegas and energy in Bangkok.
Of course, this is all just conjecture, we will have to wait and see!