Yoda unfortunately can't appear in every piece of Star Wars media, but he will make an appearance in The Force Unleashed 2.
The shortest Jedi known to the Star Wars universe has been confirmed to have a part in Star Wars: The Force Unleashed 2. Talking about Yoda, I am. I promise, that's the only time I'll do that. Must... resist... Yoda talk.
LucasArts announced Yoda's cameo to coincide with the Star Wars Celebration V convention and the 30th anniversary of Star Wars Episode V: The Empire Strikes Back. When Force Unleashed's main character Starkiller escapes from Darth Vader, he senses a powerful presence on planet Dagobah. The powerful, robed green-ish one is waiting there and guides Starkiller into the Dark Side-tainted "Cave of Evils," where Luke Skywalker defeated an illusion of Darth Vader in Empire Strikes Back.
What Starkiller finds inside, nobody knows, but Yoda says: "That what you seek, inside, you will find." The Cave of Evils could be a huge turning point for Starkiller in the game. It's also unknown if Yoda makes only this short cameo or has a bigger part.
I'm glad to know Yoda makes an appearance in Force Unleashed 2, but this would have been a really cool surprise to have left secret. I suppose PR folks have to promote their games somehow, even if it means revealing key moments. Star Wars: The Force Unleashed 2 will be released across all systems console and handheld on October 26, 2010 (October 29 in Europe).