<i>There's only so many transformations of bits people will pay money for.</i><p>Says who?<p><i>Do you ever worry we'll run out?</i><p>No. I think people will always be willing to pay for something that saves them time, makes them more money, or fulfills some other need/want.
I don't see it as a bits-specific question. It's more: will we ever run out of services people will pay for? Probably not. On the other hand, whole swathes of service classes can be obsoleted. It's quite possible that in 20 years making a website and letting it run mostly on autopilot will not be a way to make money (though I can't predict that confidently).
When we run out, we've struck upon post-scarcity and you'll have no needs that won't be attended to.<p>Wants? I'm not so sure about that part.<p>Edit: You may however, be forced out of your comfort zone as more problem space gets explored. Don't expect to be able to use Rails and Django to solve everything.