I think that is underestimating the band's fan base. Overall, the majority of their work over the last decade has gotten pretty mixed opinions from the online fan base (which, to be fair, does not always account for the entire fan base), yet many would say they are as popular now as they have ever been (except for probably '93), so I don't think tons of fans are suddenly gonna jump ship because a song or two is not inside the box they usually keeps themselves in.
And it is not like those of us wanting to hear what they could do with something like Rudess described, want them to change their entire sound. But a song or two on the next album that is a departure from their usual sound would be more than welcomed. I'd be interested to hear what they could do if they challenged themselves to think outside the box a bit. But like was just said, I think they are afraid of going backwards as far as fan support goes, as getting to where they are now has been a long and difficult journey, but again, I think they are underestimating their fan base.