The Nintendo land at Universal’s park in Japan is ready to open, and a smaller version of the land is currently under construction in California, but assuming Epic Universe gets built at all, it could be a decade at this point before it’s done, and that’s a long time to wait for the east coast.
It also seems likely, though this is pure speculation, that the agreement between Universal and Nintendo requires Universal to actually produce attractions by a certain date to avoid losing the licensing rights, and so it’s probably in the resort’s best interests to do something sooner rather than later.