Responses for your queries
1) The main purpose to increase the PF wage limit is to get more coverages for PF account and to save more. In this case no existing EPF member can quit from EPF Coverage. Even if any employee's wages is above 15000/- and already a contributing member he/she have to continue his/her contribution.
2) Yes. As per the PF notification existing employee can't quit from the PF contributions. If at all quits then when ever the inspection happens then EPF Enforcement officers will charge both the contributions to ER & including interest & penalty.
3) If any new employee is getting the basic lesser than 15000/- then PF contribution is mandatory. If at all the new employee is drawing the wages above 15000/- and if at all he had EPF account in previous organisation then he will become a coverable member only
PF is a social security provided by the employer.
Every employee should opt for that. As in central Government and PSU it is compulsory . But in some Pvt organisation they change as per their wish and will.
Regarding your querry:
1.No if he is already member then he can not quit. It is the duty of HR personnel to counsel the employee.
2. Yes. If there is inspection, you may be charged to pay both including interest and damage charges.
3. New joinee , yes. If his basic pay is more than Rs 15000/-. However if he is already memeber and join a new organisation after resignation then in that case he can not opt for that.
Please let me know if you need any further clarification.