Variety recently caught up with Star Wars veteran puppet master and voice talent FrankOz to question him about his possible involvement in future Star Wars projects. When asked directly, Oz expressed that he has been asked not to talk about it, which in itself is a possible hint of his involvement.
Variety: There are reports that you might reprise Yoda in the new “Star Wars"
Frank Oz: I feel like I’m a prisoner at war here, and I can only give you my name, rank and serial number. To be true to the people who asked me, and they are kind of my family, I have to say I’ve been asked not to talk about it. I love Yoda. I would be happy to talk to you about it at the time they let me.
Ewan McGregor also did a reddit Q&A this past weekend and when asked if he would be appearing in The Last Jedi completely ignored the question leaving it unanswered. To be fair he left all Star Wars questions unanswered though.