The big concern is when the vendors make changes that make their components not interoperate with other components on a page - we'll be watching this closely, and seek to address it vigorously. But as a user and customer of those vendors, you can do so as well, by letting them know that component interoperability is important to you.
Yes, the biggest toxin to the JSF ecosystem is the inability for components to interoperate because of low-level conflicts such as in JavaScript. To keep the ecosystem healthy, we have to play our part in getting components to "play nicely together in the sandbox" within reason. Obviously, there are exceptions, such as two layout systems. We are dealing with the level or core APIs, however.
And, as said in a different email on this thread: Other web frameworks' primary goal is to provide a complete Ajax solution. The goal of the JSF Ajax framework is to provide an easy to use set of basic functions which will be built upon by other members of the JSF ecosystem. This is markedly different than most other framework's goals.
We have a separation between a shared API and implementations. That is what make standard specifications so drastically different from most autonomous projects. We are building a platform and an ecosystem around it.
-Dan