Thanks for the news. Is this version has lxqt as de?
No, Rani. This version is, essentially, a bug fix release. It'll have LXDE desktop. Soon I'll post a really working PPA for installing LXQt easily in our Lubuntu 15.10 :)
Would it be possible to upgrade to the release easily enough when it is out? Or would that require a reinstall?
Yes, zeke. When it's out, you'll get a message about upgrading. That process is completely safe. In that process your 3rd party repositories will be deactivated to avoid package collisions. I, for instance, installed this beta over an older version without formatting and reinstalling.There's another way to check for an upgrade. Open a terminal and type "update-manager -d" and you will force the upgrade.