I can't see LR Classic going away any time soon. LR CC just doesn't have the professional tools and workflow just yet. Classic gives LR users an offline option. I am confident it will be around and still built upon for a very long time yet.
Lightroom Classic CC is the upgrade from Lightroom CC 2015 and functions exactly like the earlier version. i.e your Catalog File and your image files reside on your Computer internal or external HDD, you do not need to be always connected to the internet for it to function. It is only required that you are connected every 90 days for Adobe Creative Cloud to ensure that your subscription is up to date. If you are using the standalone application Lightroom version 6 there is no upgrade to a standalone version.
The "new" Lightroom CC is a new application and functions with your original image files stored in the Creative Cloud.
Lightroom Classic CC is a current application not a discontinued product labeled classic. To wit it is Classic, great and proven, not was Classic.
It will be around for a LONG time!