To start off, I'd like to say that while this is not 100 percent proven yet, it just seems pretty legit to me.
We have all seen the trailer where Peter's mom is saying, "Don't let her go! That's what love stories are made out of and God has placed her there for you. Bring her home, bring her home to us."
Madison has already met his whole family, on their first one-on-one date! Who else would Weber's mom be talking about? It is highly unlikely that she is talking about some random girl that she has never met!
She received a rose after she left her fantasy suite date. Peter seemed very stressed the entire time leading up to the rose ceremony when he knew that Madison hadn't arrived yet. Then, he seemed nervous to give Madison the rose over Victoria F.
Why would he give her a rose over Victoria F.? Because he's obviously in love with her.
Why did Madison come back after leaving the date? Because she obviously has strong feelings for him. This proves that they have a lot of chemistry and neither one of them wanted to let that go.
According to Reality Steve's twitter account, Madison was caught filming something with the "Bachelor" production team on February 11 in Auburn, Alabama(her hometown). What else would she be filming, except a catch up on life after the final rose? Some fans thought that she was the next bachelorette, but that has been proven to be not true.
My prediction is that Madison leaves filming right before the final rose ceremony, and Peter follows after her. I don't think that he would just leave Hannah Ann, but I'm sure he'll tell her some excuse about how he needs to figure out what's going on with Madison before making a decision. Which would explain the part in the trailer where Peter is telling someone that he's "so sorry" in the trailer.
If you haven't seen the trailer yet, go watch it here!