Could Tom Baker, who played the Fourth Doctor on Doctor Who, be the second (official) Doctor to come to Star Wars? “I’m going to be in this new Star Wars thing, you know,” he told fans at a recent convention, per Sci-Fi Fantasy Network. “I’m going down to recording some voices for this new character they’ve created for me, very soon.”
The article references The Clone Wars, but a voice part makes me think the mostly likely answer is Rebels. Or, if you want to go a little further, he could be lending his voice to a character in Rogue One.
One of Baker’s Doctor Who successors, Tenth Doctor David Tennant, voiced a droid on The Clone Wars in 2012.