Aircraft carriers are usually designed for service life of 50 years, which means Liaoning will be in service to around 2060. How will Liaoning (and Shandong) be upgraded in future depends on many factors. One important question is will it retain its role as combat capable aircraft carrier when all J15 and J15Bs retired in around 2035-2040, and how many aircraft carriers with catapult capacity will be built by then.
By 2035 to 2040, if China has 5 to 6 catapult carriers, Liaoning and Shandong may be given different roles which we cannot confirm as at now. They may upgrade them as drone carriers, amphibious assault support ships, over-sized anti-submarine ships (which is many posters' dream on type 076), or just simply as a training ship for new pilots.