Published today is an article with quotes from Jon and Trevor regarding the Rock & Roll Hall of Fame, which reveals that Geddy Lee - who is a co-inductor for Yes at the April 7th ceremony - will be providing bass support for the rendition of "Roundabout" to be performed.
There's also a hopeful quote from Trevor regarding new music:
"I think by June, July we'll pretty much have half an album finished," Rabin reports. "It's very different from anything we've done before, which we're pretty happy about, hopefully breaking new ground, soundwise."http://www.billboard.com/articles/columns/rock/7717212/yes-jon-anderson-inducted-rock-hall-interview
Update: as can be seen in the article if you view now, The Hall of Fame has issued an official statement as regards Geddy Lee's participation; he will not be performing with Yes.