Having support in X (even if only in proposal stage) will allow much easier work in the toolkit and application layers. X and Wayland cover essentially al Linux users, so we will not need to estimate how many users will benefit from implementing gesture support in toolkit X or application Y. It will make convincing project maintainers easier.
This is really important, because maintainers of open source projects don't usually care about suggested features if they're not interested in them themselves. A new feature means additional work to them - discussing the design, reviewing PRs and handling of eventual bugs. Often the person who implements a feature disappears after the PR is merged. This makes the maintainers to view all feature proposals with a grain of salt. We need to have a convincing story of how majority end users would benefit in order to make the contributions easier.
Technical skill is not enough when contributing in open source. Politics are often as important.