The Ka-52K is being bought for use on the Type 075 LHDs.
Not yet and even for foreseeable future it's not a done deal
The YJ-9 missile you are talking about has a range of 15km and a warhead of 30 kg. It is only good against tank sized targets like small patrol craft. It will be useless against frigates or destroyers.
When there is a major surface combatant comes near your ARG your response shouldn't be "let's send a helicopter". Especially heli vs destroyer doesn't tend to end well.
The Kh-35V missile the Ka-52K can carry has a range of 260km and a 145 kg warhead.
Again it shouldn't be a helicopter's job to do anti-ship mission. They take valuable deck and hangar space which for 075 are dedicated to landing support and ASW missions. And even if we really need to send a copper after a ship, it's better to send a Z-20 or Z-18 (their ASW variant would have the capability and are more suited for the mission) as not wasting a heavy gunship like Ka-52 where most of its sophisticated equipment won't come to use.
So you are comparing an aircraft which already has prototypes flying for years which is based on a proven airframe with a whole new aircraft and you think the whole new aircraft would be ready sooner?
Yes I'm comparing an RUSSIAN aircraft which already has prototypes flying for years which is based on a proven airframe with a whole new CHINESE aircraft and I think the whole new aircraft MIGHT be ready sooner.
A good example would be Su-35. It took so long for Su-35 to deliver it almost came into PLA service later than J-16 which start its development way later than former.
To clarify it I would be happy to see Ka-52 on 075's deck. It's a very capable heavy helicopter which PLA don't have a counterpart as of now. But that's only if it can deliver in a rather short time (like 3-5 years) in sufficient number, and it would be ideal if it can work well with other chinese equipment.
Not to offend anyone but with the current state of russian aviation industry it could accomplish such a quest but the chance that one or multiple instance of delaying, slow production, failing to meet certain requirements is considerable. And what ammunition would it use? (Let's ignore how russian avionics would work with chinese network cause I don't think they can solve that anyway) Are they going to use russian? In Su-35's case PLA already has a large stock of russian ammunition but for Ka-52 everything need to be imported and infrastructure, logistic, and personal needed to be established from scratch. Or are they going to use chinese? That's another couple (or more) years of works added to make it compatible with chinese missiles. Then even if everything is sorted out how long would it takes for russia to produce the numbers to fill by then at least 3 075's deck?
Finally china don't have to build a whole new aircraft. They can make a battlehawk, or made something base on Z-20 like Z-19 to Z-9. With that many effort they might as well make a naval Z-10 and that would be way better than waiting god knows how many years for Ka-52.