No. Your employer will continue to re-assess you every three years and if you are assessed as an eligible jobholder your employer is legally obliged to re-enrol you. If your employer does not adhere to the rules there can be serious consequences, including financial penalties.
You have the same opt-out rights that you’ve had previously. That means if you opt out within the given timescale, all contributions are returned and refunded by your employer, to you.