This is an important and highly plausible scenario. Everyone in this thread who feels comfortable that they can get another job at the drop of a hat owes that feeling to the existing labor market, which is fueled nearly entirely by venture capital funding. If the economy goes through another Great Recession style downturn, funding will constrain, companies that aren't immediately profitable will reduce their workforces considerably, and hiring will drop.
If, today, you work for an organization with a few dozen or couple hundred employees, but it is really run by ten or twenty "Directors", "VPs" and "Executives", they likely have full control over the majority of the capital owned by the company. They are also likely to be highly paid, and own the majority of stock or RSUs. If a moonshot expansion plan fails, they will be fine. Executing on high-risk and high-reward business ideas is 100% in their best interests.
However, if employees organize, those who instead rely on the organization to feed and shelter their families will begin to have a say in whether it's worth dumping the organization's $30M Series C into some blockchain moonshot that may never pay off.
Frankly, I don't believe they'll be as inclined to say yes. The union may instead re-negotiate to redistribute that funding to workers salaries, or to invest it in training programs. This is a good thing if you're in this industry because you're an experienced and skilled worker who wants long-term stable employment, but perhaps a bad one if you're in it to hope you hit the startup lotto and get rich after selling our your stock at 26. If you run an organization, which would you rather have working for you?