My Headcanon for how the Characters Progress in the Newsroom After the Finale

Mac takes over where Charlie left off as president of ACN for a year or two and gets the network headed down a path she approves of (back the way it was before the takeover). They finally get more successful at what they’ve been trying to do all along (including better ratings), but now that things are working out, she gets a desire to go back into producing the news because that’s where her heart is.

Don succeeds at whatever he’s on a mission to complete with Elliot, he grows more professionally to the point where he’s ready to take over ACN (which I don’t think he was quite yet in the finale - Mac was still more qualified at that point even though it’s not really her passion). He is itching to move up in the food chain, getting more interested in some major issues with the Network, and ready to make himself heard, so he takes over for Mac.

Mac goes back to being an EP for a show at ACN.  

Maybe a new young anchor will come on board who Jim will want to take on, be her EP, and make her star of a new political news show (there are more than two or three hours worth of programming to fill in a 24 hour news network - it doesn’t have to be the 8pm or 10pm hours). So, now that Jim’s on to something new, Mac goes back to producing Newsnight with Will because they have always been an amazing team.  

This also gives one of the smaller side characters a chance to finally move up and become the executive producer of the 10pm slot. 

Whatever happens, I don’t see Mac as the president of ACN forever. It’s another stopping point in her career and an amazing opportunity to set the network in the direction she wants to go, but she’ll be back to what she loves soon enough.