Honestly, I am on the fence. Like others, I was caught by surprise when this happened. At the same time, this is a critical part of my business, and I would love to keep it updated, but I am not sure how much value I would get out of the upgrade.
I went over the release notes and the biggest improvement that would help me would be the file transfer window operating faster, but I am not sure it is worth $500. I decided to just give it a try for a few days using the free license, and pay for the upgrade if it was worth it, but it limits me to 10, when I have 188.
I just posted about some new columns I would like to see, and I know I will never get those if I am not upgrading, but I have also suggested at least one extra column in about a year or two ago and it didn't seem like a priority.
From a sales perspective, I feel it would be good to grandfather your Pro users license for 1-3 months trial, so they can see what is new and get hooked so they want to buy.
The biggest challenge I see here would be the Viewers. I am not sure if people upgraded all the viewers to the new 7, if it would work with 6 if it didn't end up being worth it to someone.