I want to use my existing catalogs that I have spent years assembling.

Are you intending on using the cloud based Lr CC or Lr Classic (the normal disc based Lightroom)?

When you open Lightroom Classic for the first time, it should update the Lightroom catalog to the latest version. I have a little over 100,000 images in mine, and it took awhile. I didn't time it; I went had had lunch. When I came back it was finished. Everything is exactly like it was before, except that there are some new masking options in the gradient tools. 

The new Lightroom CC is a completely different program, that is made for mobile photography to attract customers away from Apple Photo and Google Photos.

And dSLR hobbyists like myself who don't need the complexity of Classic! :)

I have used LR (now Classic) for years.  I thought that this 'new' LR replaced it for all uses including desktop. Is that not right?

Nope. LrCC is Cloud Based and you don't have to use it. You can continue to use Classic without it.

Thank you for the blog post. Still leaves me somewhat confused.  It does say that LR CC can b used for all your LR needs.  But still doesn't answer how it loads my catalogs.  But, I agree that I am going to stay with Classic.  It works for me and I do not want to load all my photos to the cloud. Big concern, as is expressed by many contributors to the blog, is that this really means the end of Classic just not yet.

My old LR catalog upgraded nicely to the newest Classic version no problem.  But, I am in a similar boat in that I will NEVER be able to transition into the Cloud-Based LR CC because it is COMPLETELY Cloud-Based.  I would love to have a BACKUP/Copy of my Local files in the Cloud.  I would love to be able to access that from anywhere.  I DO NOT want, or trust, Adobe Cloud (or any cloud solution for that matter) to be the SOLE keeper of my originals and working copies.

I even upgraded my account to the 1TB of storage but I'm trying to get that canceled (this is really difficult by the way) because there doesn't seem to be a way to just Sync my catalog from Classic into the cloud and the new LR CC won't organize the photographs the same way I have them in my folder structures.  I would have to spend the time to reorg everything into Catalogs.

Even then, LR CC will only see what it puts in the cloud.  It doesn't seem to keep track of what is on the local drive and utilize that for editing or even file synchronization.  This means it uses EXTRA disk space for anything it pulls down to its "cache".  What does it need to cache ANYTHING for if I already have a local copy on my drive?

This concept is really terrible for anyone but the most casual of users.