I predict within 5-10 years, any tech company with an activist union will have moved most of their operations to countries where workers don't have rights. They managed to do this in the manufacturing sector. And a car factory or a steel plant is a lot harder to move than a mere office building filled with developers and sysadmins who all work remotely already.
After literally decades of outsourcing software development to other counties it isn’t much of a threat to the remaining US jobs at this point. There are various arguments about why this is or what might change over time, but unions aren’t going to change the landscape over a few years. Change like this takes decades.