How many UN member states will formally recognize Taiwan at the end of 2025?

The Republic of China has full diplomatic relations with 13 UN member states as of this writing. Those countries are: Belize, Eswatini, Guatemala, Haiti, Honduras, Marshall Islands, Nauru, Palau, Paraguay, Saint Kitts & Nevis, Saint Lucia, Saint Vincent & the Grenadines, and Tuvalu. (Vatican City, with which Taiwan also has relations, is a UN observer state.)

Taiwan and the PRC have competed over international recognition for decades. Both countries' governments officially demand exclusivity: Establishing formal diplomatic relations with one requires cutting off relations with the other. This does not preclude informal relations. For example, in 2021 Lithuania and Taiwan announced the creation of definitely-not-embassies in each other's capitals.

The most recent country to change its diplomatic stance was Nicaragua, which switched (back) to PRC in 2021.

This question uses "Republic of China" and "Taiwan" interchangeably.