Shouldn’t something this need a very high threshold for passing? Like 2/3rds of the Senate, and a majority of all states legislatures also approving of a new state?
It will never happen! It can’t happen! Not possible!
The process for statehood is not outlined in the Constitution.
Ordinarily, admitting a new state just requires a majority vote of both houses of Congress. The only exception is if a state is formed out of part of an existing state, in which case that state's legislature must consent. (U.S. Const., Art. IV).
D.C., however, is a whole different kettle of fish, because its status is already governed by the 23rd Amendment, so this would require a constitutional amendment, which isn't going to happen.