To sum up the most important points about GPG Mail 3 and the Support Plan:
GPG Mail trial will work for 30 days with no restrictions
After 30 days you will still be able to read all of your encrypted emails - GPG Mail will no longer encrypt/sign or verify emails
Once you have purchased the GPG Mail Support Plan, you will receive updates of GPG Mail 3 until the next major version is released which can but doesn't have to coincide with the next major macOS release but not more often than that. Special prices will be available for upgrades
We would really like to see you stay, but want to assure you that even if you don't like our offering there are many alternatives available. The encryption technology which is used in GPG Suite is not a proprietary one, so you are not reliant on our tools to decrypt your existing emails. There is no lock-in. In additon all of our source code is available publicly.