1. I will continue to support both HotPot and TaskChain
2. I think you are slightly confused about Hot Potatoes (the quiz making software that runs on your PC) and the HotPot module which allows you the administer Hot Potatoes quizzes via Moodle. Hot Potatoes will not change and Hot Potatoes files will not change. Indeed, I can't change them because I did not create, neither do I maintain Hot Potatoes. You will continue to be able to administer Hot Potatoes quizzes via the HotPot module, and in addition you will be able to administer them with the TaskChain module as well.
3. You will continue to he able to add a reading with Hot Potatoes on your PC. No change there.
4. TaskChain will offer the same features as QuizPort, except that TaskChanin will run on Moodle2.x
Please rest assured that any courses you have created with the HotPot, QuizPort and TaskChain modules will continue to work for a long time into the future.