I don't think a trade-down is as likely as everyone thinks. If there is a trade down, I don't think it'll be a large one that takes them out of the same talent-tier.
The back-half second/top of the third is a sweetspot that they like to have picks in. It's the range they usually trade up to, not down out of. Think Jarran Reed, Tyler Lockett, DK Metcalf, Darrell Taylor... and if they do trade down, it's usually only a few spots, like from 64 to 69 last year (which they ended up still landing Damien Lewis with).
That being said, there are a few players I could see them sticking for should they fall to 56. OC Creed Humphrey, OT/OG Alex Leatherwood, and DT Christian Barmore stand out to me.
After a minor trade down, I can see them being interested in CBs Eric Stokes or Shaun Wade should they be on the board.