I can't find any information about this anywhere else yet, and actual pricing has yet to be confirmed. CNET appears to have gotten the scoop on a "minimum 10% off" on TCL Roku 4k TVs, including the 2018 6 Series models for tomorrow 7/7/18.
Because the best value model of the 6 Series lineup is a BestBuy exclusive, I wanted to get this to people ASAP. I went ahead and placed my order for local pickup, and I plan on using BestBuy's price adjust to get the sale price when I run into the store tomorrow. Good luck all!
Edit: Now that the deals are live, I've added links to BB and Amazon.
Best Buy - TCL 6 Series, starting at $539.99 [bestbuy.com]
Amazon - TCL 6 Series, starting at $584.99 [amazon.com]