Thank you very much for you kind reply. I understand the situation.

I'm wondering following options. Which one is the best way?
 1. Upgrade my current environment (CE on Ubuntu 12.04) into Ubuntu 14.04 in a regular way. Is it reasonable?
 2. Is it possible to upgrade from CE on Ubuntu 12.04 into CE on Ubuntu 14.04 using the new release script?
 3. Clean install of Ubuntu 14.04 and use the new release script after that. But, it will cost much time to reconstruct my environment.

Sincerely,
 Yuki