Both focus on genius scientist heroes and both involve immersing outsiders in richly-constructed sci-fi worlds.
In terms of themes and visuals, the Tron franchise and Tomorrowland certainly share quite a few similarities.
From a business point of view, this arguably appears to make a certain degree of sense for Disney.
Even with Tron’s built-in fanbase, investing enormous sums of money in a third installment (especially when Tron: Legacy similarly received a lukewarm reception) likely didn’t seem like a wise decision.