Just watched the last 5 episodes today on hulu...
I was surprised to read the rumor of a 3rd season yesterday so gave it a go. After watching it though and thinking over it, I think this rumor is something meant to pop-up before the answer becomes a no. Last year, I remember reading the 2nd season was going to be ordered, then it wasn't, then it was unsure, and finally it was announced. I am thinking this same pattern is happening just with less likelihood this time around...
If it happens, I think the writer's just need to be reigned in a bit. They used the same formula as last season in the show but just tipped things differently which they can do as this show wasn't uber serious to begin with. However, the vehicle it is just didn't feel like a comfortable ride to me. The humor as many of you have said I think was too misplaced to make the dramatic elements at all dramatic. I think the writing was still clever and good but the plot wasn't involving like it should have been. The comedy tipped the type of drama seen in the first season off kilter this time more so. It didn't feel fun like it should've nor dramatic or made me feel invested seeing how the characters just seemed to be going through their required paces before the inevitable ending.
Since I invested a good portion of my day to it however, here are my thoughts on the looseends:
1) Jack Thompson Shooter
It's possible Vernon Master's is alive but judging by the type of show this is, he's put in the schemer category not to be presented as a formidable antagonist. Therefore, the most obvious guess would be a henchman (from the FBI or someone affiliated with the Arena Club) ordered by Vernon Masters to kill Jack Thompson if he wasn't back by a certain time. The Arena Club I'm guessing is unlikely after the shakeup caused by Madame Masque to key players (and Master's not seeming very willing to go behind her back until he confoundingly decides to get tricked by Thompson in episode 9 nor having time to engineer much before his demise). The FBI or usage of an SSR or government agent is of course too obvious for a show like this. Therefore, it would be someone he or Whitney told to take out Thompson should they go down so that leaves someone affiliated with the gangster guy. Regardless of the nonsensical part where the gangster boss (the guy from "Party Down" who seemed to play more of a pastiche if anything else) decides to suddenly work on the same side with the good guys (something others in this thread have already mentioned their thoughts on that I agree with), there is a point where Ms. Frost away from her work to torture one of his cohorts. The revelation of course the guy reveals common sense would say was out of fear, but being a TV show it must mean something (perhaps the writer's original idea for inserting this here?). Therefore, the gangster boss probably ordered the hit as opposed to Whitney or Vernon using one of his guys as an assurance just in case. If there is no season 3 it seems safe to assume this answer.
However, after reading post-season interviews, assuming there will be another season, this first likely possibility seems like it will be trumped by trying to take things in a different direction hence Michael Carter's resurrection.
2) The pin
The Arena Club; a gathering of power players in LA just part of something greater. A foreign influence looking to corrupt America; the shadow keeps extending to reveal more villains (the conversation between Dottie and Peggy in prison made me think this is a direction they're going). Just a trope to say the Arena club is part of something bigger. London seems to be the setting they're aiming for in Season 3. Peggy will have to return home, put light on these shadows of corruptive influence being cast down by the American establishment, and come to terms with her past and cement her place as just radiating the american spirit. The plot for season 3. I'm guessing the pin is for the Arena club and they turn it into a key when visiting other meeting areas; a cue to the audience of a villain behind a villain sort of thing.
3) The Romance
This will maintain unless Sousa is killed but I'm guessing not so much. I hope they leave this whole question on the side burner next season as this dramatic element just didn't seem to deliver this season but who knows.
4) Dottie
She was after the pin in episode 1 of season 2. The reason will be revealed the next season to tie her in.
They seemed to allude to her being influenced by Dr. Faustus in Season 1 (a retcon perhaps?). She's ruthless on her own volition but the atrocities seem to be perhaps being shifted on her upbringing and Dr. Faustus outside influence to put her in the category of unlikeable/likeable villain without a home; a means to let her pop-up randomly throughout the remaining seasons perhaps doing something for Peggy at some point or another.
5) Easter Eggs I didn't get
Was Dr. Wilke's being sent to Peru supposed to correlate to something?
Also, did those people sucked up by zero matter in fact enter another dimension? As the season wrapped up the plot without going anymore into zero matter, supposedly Dr. Strange will but I highly doubt the TV shows are interconnected with the movies enough for the movie to deliver answers the show didn't so perhaps something I missed regarding this. Oh well.