ESI Act Coverage and Contribution Period
The provisions of the ESI Act, 1948, are compulsory in nature, and you cannot exercise your option once your wages exceed the coverage limit.
However, as you mentioned, if you were covered under the ESI Act at the start of the contribution period, then despite an increase in wages beyond the coverage limit, you will continue to be covered until the close of the respective contribution period. Therefore, if you were covered in October last year, you will remain covered until March 2016, which is the close of the contribution period. You can also check your eligibility with the appropriate Branch Office of ESIC to which you are attached. For medical benefits, the entitlement will continue up to the respective benefit period only.
The ESI limit is still up to and including Rs. 15,000, and nothing has been heard in recent days about any initiatives from the appropriate authorities regarding its enhancement.