"Silicon Valley is going to leave Silicon Valley — that's already happened," Kelman told CNBC's "Power Lunch."
"The technology companies, the Wall Street companies, they're chasing the talent, [and] the talent is chasing affordable housing."
Kelman, head of the online real estate brokerage and data company, predicted an accelerating shift out of coastal cities as homeowners seek to avoid the higher tax rates of the recently passed Republican tax bill.
Densely populated and pricey cities, he said, are already losing residents and businesses.
"Google employs more engineers outside of Silicon Valley than it does in Silicon Valley, and if Google can't afford Silicon Valley, then no one can."
The "mass migration" to the center of the country is populating cities that were "economically dead five or 10 years ago," Kelman said.
Cities like Denver, San Antonio and Houston are primed to be the next hubs, he said.
"It used to be that in California we owned the future. We felt like everything was happening here first," Kelman said. "And now you see that swagger, that confidence in the center of the country. People in Detroit, people in Texas think they own the future."