Does a SGT get discharged from the Army if he transitions to becoming a warrant but later reverts back to his/her SGT rank after 14 yea RCP?

Although it's not routinely done, there could be a number of reasons that a Warrant Officer would revert to their prior enlisted rank, but the most common reason would be so they could continue on active duty and receive a regular retirement.

Specific to your question, there isn't an exception to RCP for an officer or warrant officer reverting to their enlisted rank (if held) prior to becoming an officer.

In the hypothetical situation you gave (Warrant Officer reverting to SGT and have over 14 years active duty service), and assuming you were eligible (AR 601-280, para 1-8d)*, you would have to obtain an ETP waiver in order to reenlist if you're past your RCP.
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* AR 601-280 (Army Retention Program) - https://armypubs.army.mil/epubs/DR_pubs/DR_a/ARN35366-AR_601-280-000-WEB-1.pdf

Seen it happen. Associate was a Flight WO1, then his hearing tripped him up medically, then transitioned to intel MOS, and tried to apply for Intel WO from SSG, but was told too bad so said, you failed out of the flight WO program so that was your WO chance.

Totally blows.............

In A Similar Situation, There Was A WO-1 Who Was The Maintenance Officer In My Last Company , Who Reverted Back To SSG ,
Because He Could Not Get Promoted To WO-2 For Failing A Required School .

Not sure, my assumption it depends on your contract as a Warrant Officer. I had friends in the Army who was a non-commissioned officer and went to Warrant Officer School and graduated. Once your transition to that rank and was honored for that rank as. You should honor it. Unless, you mess up and was demoted to Sergeant that could happen. Check with your Branch they have Regs to figure it out.

This reminds me of a lot of sad sacks in the Clinton RIFs. When my old man was an E-7, they offered him a direct commission (he had a masters and like 12-15 years at that time). He declined. Those who accepted were the first ones cut in the RIF, the reasoning being that they could go back to being E-7s...after losing a bunch of years of progress as NCOs. Since they successfully/honorably held the rank of Captain, they'd be able to retire as Captains, but since my dad said no, he retired as a Sergeant Major. I know which I prefer! A retired SGM gets treated like a colonel for life!

Sort of an odd story. While assigned in Frankfurt, our office was in the IG Farben Building, aka the Abrams Building. I knew an SFC who was in the legal office (IIRC), but I noticed that he had wings. I assumed they were crew wings, but after looking at them one day I realized that they were an aviator badge. He had been an OCS grad who served as a pilot in Vietnam, and then was subsequently RIFed. It happens. I didn't see him for a while, and one day he was in his greens with WO1 bars. Apparently he had gotten a call from aviation branch and was offered an appointment as an aviation warrant. It seems they needed qualified people in his aircraft. He was headed back for a refresher course, then off to the Army as a Warrant.

I was enlisted in the Air Force and was commissioned after 7 years of service. After 7 years of commissioned service there was a reduction in force (RIF) and I was let go. Since I went directly into commissioned service from enlisted the Air Force had to allow me to revert to my enlisted rank (E-5). I served 2 more years, got promoted to E-6 and then was offered an early retirement.

Must be E6 and a rigorous program to become a warrant officer plus the credentials for applying then getting picked is no easy task. Like eating chicken feet soup finally getting fried chicken and going back when completed. Probably messed up badly or very poor performance as a WO, but most likely an article 13 that demoted him. Don’t play the he/she/it crap.