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You have the articles covering the concept:
Beta Test covers it as a thing that exists (media notes/useful notes in general cover Chairs topics that still benefit from some explainer info)
Perpetual Beta covers the trope where the line between "Extremely Lengthy Creation that still lets people try what's already done", "alleged full release", "half-complete project the creator might eventually get around to finishing", and full blown vaporware become blurry.
Edited by Scorpion451

Do we have a trope about the phenomena of Early Access, Open Beta, and things like that? I know we have Beta Test, which describes the development process, but I wasn't able to find early access/open beta as a trope. There's also Perpetual Beta, when the developers never really finish the game, but that's (ideally) not the same thing. However, it's a very popular way of launching PC games in the last 5-10 years, has a lot of success stories and controversy and probably deserves description. I'd be willing to take it to the launchpad.