The Empire very clearly operates under a very strict chain of command, and if Orson Krennic is taking orders from Darth Vader, then it’s entirely plausible that we will see the man Vader takes orders from as well.
Rogue One takes place during the height of The Empire’s power, and as such it would make plenty of sense for the face of the Imperial forces to pop up — whether it be in person, as a hologram, or even as a work of art.
Technically Ian McDiarmid already came out and admitted that he will not appear in Rogue One as the dreaded Emperor Palpatine, but that does not inherently mean that the character won’t make an appearance at some point.