Tomorrow will be release PHP 7, how Ubuntu plans to support it? It will be available at least in official LTS repository or we need to wait the next Ubuntu release?
The new upstream PHP 7.0 won't be supported in existing releases. The policy on bringing new stuff to existing releases is very clear on that -> only security releases go in. You can read about the Ubuntu policy here: https://wiki.ubuntu.com/StableReleaseUpdates
The good news is that Ubuntu 16.04 LTS will be released with PHP 7.0 packages. Nish from Canonical made an heroic effort to push my Debian packaging into Ubuntu 16.04 and he has also updated many packages that depend on PHP and cleaned up the rest that doesn't support PHP 7.0 (yet or never will).
If you want to use PHP 7.0 on older Ubuntu releases, the only way is to use some external means, like my
ppa:ondrej/php PPA that carry co-installable PHP 5.6 and PHP 7.0 for Ubuntu 14.04 and later.