I read somewhere that in order to use new forum,users are required to update their email and it should be functional.
Don't need a new email, just one that can get emails that you control.
Does it means new forum will have feature to login via email?
Not in the current beta.
Can we test the new forum if we update our email?
Yes, go to beta.bitcointalk.org and reset your password. You will get an email telling where it tells you how to change your password (for beta only), and than login afterward.