A study in 2000 found that a household in California used 132,000 gallons of water per year. 132,000 gallons of water weighs 550 tons, and seawater is 3.5% salt, desalinating 550 tons of water would (optimally) produce something like 20 tons of salt.

To supply 10 million households with drinking water from sea water, then, produces 200 million tons of salt. The current global salt market is 250 million tons, at a price of about $50 / ton. I find it unlikely that the market would bear dumping that much salt on it at a price that would make producing the salt worth it.

Disposal is probably a cheaper course.