I broadly agree with Ryz05. With cruise missiles, submarines can handle many of the missions that carriers have been tasked with such as coastal and deep inland strikes on less hardened, static targets as well as surface ships, freeing up carrier strike aircraft to hunt moving land targets, targets of opportunity, and hardened targets that require very heavy precision guided munitions to take out. Granted, cruise missiles are expensive, but letting submarines take out many of the more pedestrian targets (I don't mean using cruise missiles on machine gun nests and field kitchens)-and air defenses- frees up, to a certain extent, highly-trained aircrew to go after targets that missiles can't handle.
Using so many submarine-launched cruise missiles in lieu of carrier-based air strikes does raise the issue of sustainability. Even at the highest sortie rates in wartime, carriers can sustain air strikes for at least a few to even several days without replenishment, whereas until recently no submarines carried more than about 2 dozen cruise missiles, and those on the Oscar/Oscar IIs were anti-ship, not land attack. A few submarines so equipped MAY be sufficient to deal with a carrier battle group (potentially very useful to China), but even with land-attack missiles aboard, such a force just can't do enough damage, let alone keep it up, on land targets compared to a carrier. Now, the conversion of the first four Ohio-class SSBN to SSGN each with 154 cruise missiles open up an entirely new world of possibilities. Many more such conversions would be necessary, though, to create a force of such SSGNs large enough to appreciably lighten the strike burden on the carriers, for American purposes, anyway.
I am not saying that such boats could replace aircraft carriers, but given their heavy missile load-outs a few of these operating with a carrier or two could considerably reduce the strike load on the carriers, allowing them go after targets cruise missiles can't handle and to mop up targets that cruise missiles didn't finish.
For Chinese purposes, it would make sense to have a large force of cruise missile-equipped submarines, both for land strikes and to deal with surface ships-and it might reduce the need for China to ultimately seek carrier parity with the U.S. in the decades to come if such submarines could fulfill some of the taskings of the aircraft carrier. A carrier could be reserved for the more difficult strike missions requiring human finesse, or, as Ryz05 observed, used Russian-style to protect their SSBN bastion in the Yellow Sea/ Bay of Bohai.