As a contractor, I once had 9 ongoing projects for about 2 weeks, and that was an insane amount of work and context juggling. Handling 30 active clients for a year, let alone a career, seems impossible.
So either the clients aren't asking for much (which is most likely) or I'm missing something. I assume many bigger companies would happily replace a staff member, or a staff member's valuable time, with a ~30k/year contractor. Critically, these companies wouldn't feel the need to "get their money's worth" by keeping the guy busy every day. However, the smaller companies most freelancers see as their bread and butter are more cost sensitive, and will nickel and dime you as much as possible.
Are there enough big, monied companies to constitute a "storm", which I take to mean a shift in the business model for freelancers and boutique contractors? I dunno about that. I'd guess no, offhand.
Seems like DesignJoy has create a neat niche, which is awesome for him! I don't think it scales to the "disruption" level as this article implies.