This type of question is starting to become somewhat irrelevant since all new stuffs know they have to embrace VoIP as part of the future tech landscape. Chrome OS is no exception. VoIP will, according to me, thrive on it.
Reasons are numerous. First, it is Linux-based and therefore open. VoIP services and developers won't have to wait for clearance and APIs. Second, Sun is trying to add Java support, and when you have Java, you have a wide platform for applications. Third, it supports Flash, and some VoIP services deploy Flash applications, such as the recently-reviewed TringMe. After all, Chrome OS will be an operating system for Web and communication.
As of now it does not support Java PERIOD.
It supports JavaScript, Flash and Native Client in the future.
Kick the tires and light the fires, problem offilcaily solved!