Given that there's typically confidentiality requirements in these types of contractual discussions, it's likely that Universal at least brought up that they were likely to be looking at a 3rd dry park in a 5-15 year time frame. I doubt they'd be able to be much more specific than that though back in 2014-2015.
@Disneyhead was pointing out as far back as 2013 that his sources at Universal said that they were trying to get back the Lockheed land and were looking at a separate 2nd resort as their favored mode of expansion versus buying up properties around the 1st resort to extend CityWalk. In those posts he brought up the 2023-2025 timeline for the next dry park assuming of course that they got the land within 3-4 years before that.
It sounds as if that's the rough guess that Universal could give Nintendo in their talks.
Still, the current Universal leadership negotiated the Marvel contract and Harry Potter contract, both of which gave zones of exclusivity and allowed possible expansion to multiple US theme parks.
Until someone actually shows evidence that they didn't negotiate the same way with Nintendo's rights, then I'd be inclined to believe that they mentioned probable/possible expansion and negotiated in that option as they did in the previous major rights agreements.