No, drop-down plan selection like featured here on Joomlapolis is not yet available. We've plans to later release the plugin we're using to accomplish this after changes have been made (currently hardcoded for internal use).

I think you might be able to somewhat accomplish this if you used a new CB plugin and the on before registration from trigger to load jquery and alter its appearance entirely with jquery, but that would be something for advanced developers.. CB Conditionals (available to professional subscribers from incubator) usage of step by step registration form could be used as an example of the triggers usage.