Not obsolete in the sense they are no longer competitive but obsolete in the sense there isn't much sense to procure them further, once J-XDS hits the LRIP phase why would the navy keep buying J-35s? The navy unlike the air force doesn't operate thousands of fighters so it doesn't take forever to replace old ones nor do they really need a hi-lo mix of fighters, at best by 2030 PLAN would be operating approx. 132 fighters on carriers plus a dozen or two extras for spare and training. As Cute Orca said, the navy only have so little fighters that they are willing to spend more money on the latest and greatest so IMO once J-XDS hits the market no more J-35 would be procured. So, if 2D TVC J-35 are ready the same time has J-XDS why would the navy buy 2D TVC J-35 and not just straight up the much better J-XDS?
Because:
#1 - Unless the development works of the J-XDS and its carrier-based variant (let's name it J-XDSH) are conducted simultaneously and progresses at the same rates from-start-to-end, the J-XDSH will enter service with the PLAN after the J-XDS with the PLAAF. This means delay of one or a couple years is to be expected, thanks to the more stringent and challenging technical requirements for carrier-based fighters than their land-based counterparts.
#2 - The J-XDS is expected to be more expensive than the J-35 by a not-insignificant margin, from procurement to operation and maintenance expenses. There's also the key factor where the PLAN is already being weighed down by many other concurrent projects which are money-eating monsters (mainly CVNs, next-gen surface combatants and next-gen SSNs/SSBNs).
#3 - The PLAN isn't aiming for all-J-XDSH carrier-based fighter air wings (CVWs), similarly to how the USN isn't aiming for all-F-35C carrier-based fighter CVWs. The F-35Cs replace the Hornets and complement the Super Hornets, whereas the upcoming F/A-XXs will replace the Super Hornets and complement the F-35Cs. In retrospect, the J-XDSHs will eventually do the same to the J-15s (on CATOBAR carriers) and complement the J-35s.
#4 - Not every mission requires the J-XDSHs. Generally, for low to moderate-intensity/risk missions (e.g. CAP, plus anti-ship and/or land-attack missions where aerial supremacy has been obtained), the J-35s are pretty sufficient. Therefore, the J-XDSHs will be the "high-end" combat units that go toe-to-toe with the main/vanguard enemy aerial forces, whereas the J-35s will become the "low-end" aerial combat workhorse of the PLAN.
#5 - With #2 and #4 in mind, having a mixed carrier-based fighter CVW of J-35s and J-XDSHs is also a much more cost-effective solution to the PLAN's demands for the foreseeable future.
TL; DR - Yes, the PLAN demands the best for their fighters, thanks to them being the first to face the enemy forces head-on in the WestPac. But that should be done reasonably and within budgetary constrains.
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