I have LR 6.6 stand-alone. I’m reticent to drink the Adobe Kool-Aid, but am also looking to the future. Since I teach workshops and do presentations, I want to stay current. So, despite my initial “Adobe can kiss my ...” comment, and the fact that I abhore the subs model, it looks like I don’t really have a choice.
So, will LR CC over-write my standalone version of CC (just in case I have a change of heart six months or a year down the line)? I’ve scoured the ‘net for an answer, but, given the confusion over what was LR CC and what LR CC is now, searches are coming up blank.
The answer is no. However, it's never so simple, partly because Adobe make it difficult to know exactly what you are asking.
LRCC is generally being used for the brand new PC/Mac application Lightroom CC. But what you have been using before is now called Lightroom "Classic" or LR7.
Let's assume you mean to stay "Classic". When you install "Classic", the installation via Adobe's CC app
defaults to removing previous versions. The Advanced Options let you keep them. When you open a LR6.6 catalogue, "Classic" makes a copy of it and upgrades the copy, which is good. It also appropriates its previews folder. If you want the LR6.6 catalogue to keep its previews folder, temporarily rename it before upgrading. This forces LR7 to build its own previews folder, which is what I prefer (preview generation is much faster in LR7).
But if we assume you do mean LRCC, the new desktop app, it installs separately and does not take over any existing content. It will populate collections / albums from smart previews that you may have synced to Adobe's cloud. There is a File > Migrate Catalog command which allows you to import a LR6/7 catalogue. You would use this if you wanted that catalogue's contents in LRCC, which will sync originals to the cloud. Because LRCC is now managing your originals and syncing them, Migrate Catalog also disables the LR6/7 catalogue's ability to sync. Personally, I won't do Migrate Catalog - I don't want my originals in the cloud, and am happy using LRCC as "Lightroom Mobile on my laptop".
A lot of detail there - hope it answers your questions.
John