He *can* gain 30 more pounds of muscle. He's only 27-28 and won't hit his absolute peak for 8 years.
Will he look as good at 260-270 as he does today? I don't think so. A lot of guys, IMO, looked way better when they started than when they finished. Levrone 1992- insane. Wheeler 93- insane. Early Shawn Ray- Insane. All of these guys got a cloned bloated look when they added 20+ pounds (hi insulin!)