It won't affect current senior recipients. The enhancement will increase the replacement rate and it will increase the amount of insured earnings that are covered. It will accumulate over 40 years, essentially. It will take someone starting in 2019 over 40 years to accumulate full benefits.
The resources for those benefits are coming from the contributions of employees, employers, self-employed people, and the return on investments. Per the legislation under the Canada Pension Plan, these enhancements are fully funded. They are essentially paying for themselves as we go.