Any chance to survive after "Apple Developer Program membership will be terminated" message? I've got "your Apple Developer Program account has been flagged for removal" message on the 3rd May 2019. On 15th May 2019, I've got the "your Apple Developer Program membership will be terminated" message. 
Apple does not share specific reasons for that decision, as usual.

However, as of 20th May the account is still active: I can access it and make changes.

Since the 15th of May I've removed from sale all apps that could have caused Apple's anger. I've disabled all corresponding In-App purchases. I've deleted most of the apps. I can't delete one of them because there's an In-App purchase with "in Review" status.

Is there still a chance for canceling the termination of my membership? How long does it usually take to terminate a membership?

Waiting for death is sort of worse than the death itself.
Only Apple can answer your queries.


  Is there still a chance for canceling the termination of my membership? How long does it usually take to terminate a membership?


There's no documented rules for this, and it's totally upto the concerned team(s) at Apple to take calls. As far as one can understand, it is taken up on a case by case basis.

To get answers to any of your queries, it's best to contact Apple Developer Support:


Support - Apple Developer
Worldwide Telephone Support - Apple Developer