According to The Wrestling Observer, while details on the exact matches are scarce at this point, Vince McMahon has reportedly decided on the top 6 matches at WrestleMania 32, and Daniel Bryan is currently not factored into PPV plans. This is because WWE officials are unsure whether or not he will be able to compete.
As for Sting, Vince is reportedly against the idea of Sting vs. The Undertaker, so that match will likely not happen. WWE does have plans for Sting, and it could include him competing at WrestleMania or a Hall of Fame induction as he now lives in the Dallas area.
As for John Cena, Vince McMahon has his opponent picked out, but that name has yet to be revealed.
WWE still wants The Rock and Ronda Rousey vs Stephanie McMahon and Triple H at ‘Mania, or two singles match with the men and women. This of course all depends on how willing UFC is to allow Rousey to compete at WrestleMania.