Yes, ESI contribution is necessary during the current contribution period.
Explanation
If someone is getting ₹14,500 in the month of November 2012 and their salary increased by ₹1,000 with effect from January 2013 onwards, their salary is now ₹15,500. They will continue to be a member up to March 2013, and deductions will be made on ₹15,500 until March 2013. After that, they will be exempted from ESI. Employees will be exempted from ESI after March or September if there is an increase in between.