I doubt more than a very small handful of operators will ever put a First Class cabin on the 787-8/9 - the economic case for doing so is rather poor. International First Class demand just isn't what it used to be, especially given the cost belt-tightening at multinationals and the improvement of the modern Business Class product to a point where the step-up to F has little extrinsic value.
Heck, look at the A380 - the bird can easily accommodate a sizable F section, but most operators are putting LESS F seats into the 380 than is used on predecessor longhaul flagships.