I don't expect the first batch J15 to have major upgrade due to their extensive training use. Up to now, training is still the most important matter as a large pool of pilots (for CV16, 17 and new carriers) need to be trained especially on the landing skills.
Each current J15 would likely be assigned to not less than 2 pilots, or three. With intensive training of 200 hours a year for each pilot, not less than 400 hours of air frame life would be depleted annually, or >4,000 hours for 10 years (2014 -2024).
Building new aircraft (J15B?) might be more cost effective than MLU aircraft with limited air frame time.