[S2 spoilers] My theory about the leadership in Season 2
Before there was a discussion about why Vi was wearing the golden Sherrif's badge in that teaser from few days ago, but after the trailer droped it all makes a little bit more sense, at least to me.
I believe that Vi could be THE Sheriff... for at least the first part of seasone 2, and here is why I think that.
After the ending of the first season we know that we are now left with most of the council dead, thus leaving a large power vacuum in Piltover. We already see Ambessa stepping in to fill in the void her daughter Mel left behind (asuming that she really is dead or greatly injured), which makes sense. Medarda is one of the most influental families in Piltover, so it only makes sense for another member of the family to step in and continue from where Mel left of. Of course, we can asume that Ambessa did that not just because of power but more because of wanting to avange her daughter, but then we can ask what about others?
That led me to believe that Caitlyn steped in in place of her mother since she's Kiramman and thus still holds great influnece over Piltover and it's politics, no matter if she's happy with being a counciler or not. That would also explain her sudden change of outfit we saw in the earlier teaser since her mother also used to wear something simular. We can asume that the begining the beginning of season 2 is taking place shorty after the events of season 1, just how we saw at the start of the trailer. That would even further explain Caitlyn's sudden change in her clothing because she's not just wearing that to pay respect or to remeber her now decided mother, but also because she's now a counciler as well, just like her mother was.
Now, if Caitlyn is indeed a counciler at the start of the new season, then that still leaves the role of the Sheriff of Piltover still to be filled. That's why I believe that Vi will be that someone to get that role after siding with Piltover. She probably isn't the biggerst fan of the decision, but is entirely possible. Yes, realistically there are other people in Piltover itself who with their influance can get to the Sheriff's badge insted of a Zaunite, but Vi would have people to back her up in her new possition, mainly Caitlyn now that she's an actual counciler and maybe even Jayce considering that he survived the attack.
I expect that as the season 2 goes on that we will see more new characters appear to fill in the role of previous councilers (for example the house of Ferros since they are too a very, very powerful family according to the lore of the game). I also expect that Teimerdinger too will come back and take back the spot in the council that he used to have for so many years, but now with the new wistom and understanding that he got from his time in Undercity.
Ps: Sorry for bad English, it's not my first language. Feel free to point out any mistakes since I don't write often in here... or anywhere really. I'm just really inlove with the show and wanted to share some of my thoughts from how hyped I am for new season! Though I'm sad that this is the end of Piltover and Zaun story...