That Is pure guesswork.
There is no reason why j10a would not be designed to last at least as long as j7e for example. Meaning 30 or so years.
And there is no reason why they could not be upgraded over the years. Old j8d saw a pretty potent upgrade, getting new avionics. J11a got support for new weapons and got new passive sensors.
J11b are getting new radars and they are more or less contemporaries of j10a.
The air cooled aesa array used in pakistani new block jf17 could for example be used as a basis for a radar to replace existing j10a radars.
I would be very surprised if any one unit of j10a has its planes retired within the next ten years. At the very least 10 years.
The J-11B Type 1475 radars occurred after the J-10A's Type 1473 radars. So you can say its earlier, earlier by a number of years.
To upgrade the J-10A, the entire radar needs to be replaced. That's entirely possible, but it would be more expensive, then say, upgrading only certain parts of the J-10B's radar to match the J-10C.
And then you have to figure the cost of doing this versus the remaining life of the airframe. I don't think you can upgrade only parts of the J-10A's radar, that will be like mixing 2005 electronics with 2018 electronics. Its a poor match, like adding the latest video card on your 2005 PC. It has to be whole or bust. If you still want to go through with it despite the remaining hours on the airframe, you would have to overhaul and strengthen the airframe to add more frame life into it. But remember the cost of these upgrades, both radar and airframe, is going to come out from your budget of buying entirely new aircraft. You are going to have to decide lets say theoretically, the cost of having 10 J-10A MLU vs. 1 J-20.
As for the J-8D, they had their original radars which I think used a cassegrain antenna replaced completely with NRIET's Type 1471 radar, which uses slotted planar array. As you can see with the numbers, the evolution progression of the radars went like this: Type 1471 -> Type 1473 -> Type 1475. They all used slotted array, but the back end electronics could differ significantly in modernity.