The escape hatch is if contributors are asked to assign their copyright, which then centralizes decision making with the entity holding the copyright. Which works if you trust that entity (eg, the FSF), but it most definitely has the possibility to go wrong if the copyright holder makes license changes down the road which you disagree with.
If you relicense an existing project, it doesn't invalidate the prior license on the prior version, so any versions you release under GPL can thus be used within GPL rules, unless you have a contract stating otherwise with a specific entity (and if they wish to dissolve that license and use the work under GPL rules, they have that right too)