THe case for Magna
Well since there is a lot of worrying going on about the game getting delayed lets just switch the topic to how the game will connect with the comics like they have said it would.
Probably one of the more likely ways it could connect would be that Magna's group appears in the comic.
So lets just go over how realistic it would be for them to appear. They have said that season 3 will take place around the same time the comics currently are. I have a feeling it won't be exactly where they are right now but more or less around the time that the timeskip was going on after AOW.
So what are the chances Clem could run into Magna's group during that time. Well Magna said she originally was from Richmond and once the Apocalypse started she and some others started traveling towards D.C. because the government was telling people they would be safer in the cities. Well they didn't make it and ended up finding a group hunkering down at a nursing facility. In the comic they never specified where the nursing facility was other than it was closer to D.C.
Magna stayed there for several years but the place started to turn bad and several of them decided to leave. They were out on their own for seven months before their first appearance in the comic.
If Clem is to run into Magna then season 3 would need to take place fairly close to the D.C area. Richmond is only 100 miles away from Alexandria and Magna said the nursing facility was even closer to Alexandria/D.C then that. Chances are during that 7 months they were out on their own Magna's group slowly began to inch their way closer to D.C. and weren't running around all over the great state of Virginia.
The biggest case against seeing Magna in the game though was that Andrea asked Magna how many people they had encountered during their time out there and Magna said none.
So I think the chances are slim we would encounter Magna's group after they had left the nursing facility. Clementine encountering the actual nursing facility before Magna left would be a stronger possibility though.