My guess... This will tie in to the corruption of Numenor. He'll make the rings at their forge, which will also tie into the 'sinking' of Numenor.
The question is if he will also use Mithril or something else. If he uses Mithril, then did he already pocket a fragment, or will that tie into Numenor coming back for round 2? Will he make the One Ring first, but wait to use it, or save it for afterwards? My guess is afterwards.