If you haven't already, it's time to adjust your way of thinking about what a website actually is. It's not what it was. Your website of 2013 should have one distinct difference baked in versus prior iterations… It needs to be device neutral. No matter whether someone views it from a desktop, tablet or phone, the experience ought to be similarly effective.
One caveat at least for now is that most companies should have a trimmed down version of the site for mobile users as mobile requirements are often less encompassing. Very few companies though, particularly b2b ones are anywhere close to delivering a consistent experience across devices. What's at stake is everything if you believe that your web presence will be a significant driver of revenue into the future.
All signs point to the fact that desktop engagement time is declining and mobile usage is on an upward trajectory. How does your site look today on the millions of iPad minis that will be sold during Q4?
I recall the early days when we had to convince people that they ought to build and market their initial website. I watched mobile sputter during it's early adoption years. With each evolution that's occurred, the early adopters have ultimately leapfrogged everyone else. We are now beyond the early adopter phase. Does your organization have anything to show for it with respect to cross-device functionality? Irrespective of the answer, the time is now to make a commitment and divert resources in this direction.