No company is going to be able to put Dunhill's blends back on the market without going through the FDA "substantial equivalency" process. Nobody knows how burdensome the FDA process will be (hint: probably excessively burdensome, and intentionally so).
It's highly likely that Dunhill blends are gone for good. Make no mistake, the FDA is attempting to regulate smoking out of existence. It's pure zealotry, and a "moral panic" rather than a rational action, as I've discussed on this forum. Of course, there will be pushback, and pipe smoking and other forms of smoking will continue, but there will be casualties, and Dunhill blends are on the chopping block.