Answering about Mountain Lion at this point would be speculation, not permitted in these forums.
You have to understand that FCE was discontinued even before Lion was released. It is not supported on Lion. Many users have attempted to install & run FCE on Lion and have either failed or had problems with the results. The few that seem to have successfully used FCE on Lion basically already had FCE installed on Snow Leopard before upgrading to Lion.
FCE was EOL (end-of-life) as of June 2011. Final Cut Pro X is the current solution.