According to tweets from @PaulGAllen and @PeterDiamandis, Deep Challenge should arrive at the bottom around 14:40 PST.
Edit (14:50 PST): No word from @PaulGAllen since 14:20 PST, when he noted Cameron was at 32160 feet and "not long to seabead now". I hope the people on the support crew are just really busy because Cameron is touching down on the bottom!
Amazing that it is working. The engineering must be interesting.
Edit: Apparently the DC weighs a tenth as much as the Trieste (the original bathyscaphe), including all the instruments. Less than a lifetime. . .
"The hull, complete with its hatch and viewport, was tested twice in a pressure chamber at Pennsylvania State University to an equivalent full-ocean-depth pressure of 16,500 pounds per square inch (1,138 bars). It passed both tests. Twenty-two strain gauges attached to the sphere gave data that indicated the sphere could withstand up to 140 percent of the test pressure without buckling."
I'd love to see a dissection of the submersible once they bring it back up. It'd be interesting to see if there were any seal or structural failures.