Adobe could easily gain me as a customer for Lightroom 6 (standalone not CC) if I had their assurance that buying it would be a good investment of money and time. Since organizing and tagging one's photo collection can take significant time-- it wouldn't be worth it if Lightroom 6 is the last standalone Lightroom product ever (as everything moves to the Creative Cloud (CC)). I know Adobe's motive is to move everyone to CC but that doesn't work for me.
It doesn't foster much trust or goodwill when Adobe doesn't communicate with their customers about the longevity and future plans for their products. It's easy to see that Adobe wants to go CC because it's best for them. And I haven't read anything about Adobe guaranteeing users of Standalone Lightroom that they are in good hands and can confidently trust that they will be taken care of: meaning that Lightroom standalone won't be dropped or abandoned and we will see a Lightroom 7, 8, 9, etc. Ideally, Lightroom CC users will get updates on the fly in the cloud and maybe once every 1-2 years, Adobe packages up the latest updates and releases it in a standalone product. But I can easily see Lightroom CC receiving updates in the cloud and Adobe letting Lightroom standalone languishing into oblivion.
Ideally, I wish I could get a straight answer from adobe but perhaps that's their game; they don't want to assure Standalone Lightroom users of anything, they want us on CC...
Unfortunately I can't be a customer of Lightroom without good customer service communication and assurances...
And I am an Adobe customer of other products (but no, not CC).
Adobe has said that Lightroom will be a standalone product for the "forseeable future", whatever that means.
I'm not really sure what your concern is about Lightroom CC, is it just that you object to the monthly payments, or do you have other objections that would prevent you from using it if that was the only choice for Lightroom? You made a comment about how tagging is a significant amount of time and it wouldn't be worth it if Lightroom 6 is the last standalone product ever, but you could transfer the tags to Lightroom CC very easily.
You won't get an answer from Adobe (do any businesses make their future business strategies public knowledge? Adobe doesn't owe us that), and any other answers you get will be unfounded speculation.