The chances of Vision appearing depend on which direction Joss Whedon takes the sequel in. However, it would arguably make the most sense for him to follow The Ultimates and have Hank Pym create early versions of both Vision and Ultron, thereby leaving the door wide open for both to be fleshed out in future instalments.
Many fans were hoping that Agent Coulson would be brought back as the Vision, but his appearance in Marvel’s Agents of S.H.I.E.L.D. TV show may have put an end to that. Regardless, Vision is a great character and the androids’ complicated relationship with the Scarlet Witch is another interesting possibility to be explored.