In 1997, it was expected to be launched in 2007 for a budget of 0.5 billion $. It has since been rescheduled many times. As of the first of March 2019, NASA expects to launch it on the 30th of March 2021, for a budget of 9.66 billion $.
Question: When will the JWST be launched?
This resolves when the JWST is mounted on a rocket and the rocket engines are ignited with the intent of taking off. It also resolves if the JWST reaches space (defined as an altitude of 100 km, aka the Kármán line) through any other mean. The question resolves ambiguous if there are definitive reports that JWST is cancelled.
For the purposes of this question, any telescope that has ever officially been called "JWST", has a 6.5 meters honeycomb mirror, and is put either to L2 or L3, counts as the JWST. However the final telescope needs to be sent in a single piece accounting for >90% of its mass, otherwise this resolves ambiguous.
This closed binary question asked if the JWST would be launched before 2020. It closed in July 2018 at 1%.
This still open question asks if the JWST will be a success, conditional on launching.