I think J-10C is at the point where marginal improvements in air to air capabilities are not cost effective. The only big capability leap I see is the integration of PL-17 which should be feasible since it is not heavier than some of the anti-ship/surface weapons the J-10C already carries.In terms of structural improvements that couldn't be retrofitted to the existing air frames, they could add conformal weapon bays for AAMs and ARMs, more signature reduction measures, more cooling and electricity delivery capability. The WS-15 could be added too if they were really ambitious. The J-10D was rumored for years. I think there is a decent chance PLA evaluated the concept too. But with the J-20, it probably went to the way of the J-11D.
A fan CGI:
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What would be really valuable would be an EW variant optimized for S/DEAD. It would make it an almost unique product on the market. Even just one centerline pod covering mid band would be sufficient for most countries that don't face layered multi-band ADs (the AESA radar also covers high band by itself).
Of course, the PAF might prove that this is completely unnecessary if they DEAD some S-400s tomorrow...