So there aren't many theories on Fuller House, but there are some about Full House that I will address here. There will not be spoiler alerts during this part of the post.
The biggest theory is that "uncle Joey" is the real dad to the Tanner girls. I know it seems crazy, but it makes a lot of sense and I'll explain why. Joey is the only man in the whole series that was a blonde like the girls. So how did Joey father three girls with the wife of another man? Well the theory states that Mrs. Tanner had an affair with Joey and fathered the three girls. The theory goes on to say that the only reason that Joey moved in for so long to help with the girls without being blood related to Mr. or Mrs. Tanner is because he wanted to help out with what he thought were his kids. Then the theory also stated that Joey may have also fathered uncle Jesse and aunt Becky's twins.
The second biggest theory is that mother didn't really die but instead the series is some weird, twisted version of an alternate universe created by her to deal with the loss of her whole family. This seems more far-fetched than the first theory, but then there was another version of this theory that states that maybe just Mr. Tanner died and the series was her thinking about what life would look like if her husband survived. There is yet another version of this theory that the series in purgatory and that they think the mom died.
The only Fuller House one I can find is that the series is similar to the Truman Show in the fact that the cast knows that they are in a TV show and honestly don't care. This one is actually true. If you watch the series they actually look at the camera. One of the times I actually remember them all doing that is when they mention Michelle "building her fashion company." It was a moment where they poked fun at the fact that The Olsen twins were the only main original cast members who didn't return.
The last theory is that Michelle doesn't exist. The theory goes that Danny Tanner made her up to deal with the loss of his wife. This one really doesn't make sense because she is such a big part of uncle Jesse's life that she has to be real. And plus there was an actual kid!
OK, on to the predictions and my thoughts on the Fuller House series. I found parts unbearable, stupid, silly, and crazy. I think that the only reason why they want DJ and Steve together is to make it like the original, but it's not! I actually like DJ and Matt together, and let's not forget Steve was supposed to get married to CJ. If you are keeping score, DJ helped end two relationships just because she didn't know who she wanted. She also broke Matt's heart because she again didn't know who she wanted.
I honestly don't think we saw the last of Matt and CJ. They may not have big roles but they may come back in cameos. With Steve away it may be fun to see CJ and DJ bump into each other. I also want to see Matt fight for DJ a little more since it was really Steve who pushed his way back with DJ. I think that DJ just likes Steve because it's comfortable.
I think they will try to kick the original adults out of the series again during the up coming season. I like it when the girls and their kids are the main focus.
Sorry for the kind of short post, but there's not much to predict. It's kind of easy and there's not much to go on.