The United States has had 50 states since Hawaii was admitted in 1959. There have been unsuccessful movements to add states (or break an existing state) throughout the history of the US. Article IV, Section 3, Clause 1 of the constitution defines admission requirements:

New States may be admitted by the Congress into this Union; but no new State shall be formed or erected within the Jurisdiction of any other State; nor any State be formed by the Junction of two or more States, or Parts of States, without the Consent of the Legislatures of the States concerned as well as of the Congress.

Most notable is Puero Rico, which is currently a US territory and has had multiple unsuccessful movements. The most recent attempt was a vote in November 2020 in which 53% of Pureto Rican voters voted in favor.

Resolution Criteria:

If states are admitted and leave in the same act of Congress, and the resulting count is still 50, this will not resolve. For example, Alaska leaves and Puerto Rico joins as part of the same act, this will not resolve.

If at any point before 2030, the count of states in the United States changes to a count other than 50, this will resolve YES.

If at midnight EST on December 31st, 2029 there are still 50 US states, this will resolve NO.