It is hard to tell how big this is, but there are a few things you can tell that it is NOT. It is not a submarine, because the sail is too big. It is not an arsenal ship because it is too small and there are no long flat stretches to house the VLS tubes (that's the same reason it can't be an upgraded 055 variant as Motif mentioned). I think it's just a small test platform for a Zumwalt-style tumblehome hull and stealthy deckhouse. Who knows where PLAN will go with it, it could even be a private venture, but PLAN will probably do sometihng different instead of trying to mimic the Zumwalt and its role too directly. The Zumwalt has been an expensive fiasco for the USN, don't think PLAN wants to repeat it.

If an enlarged version of 055 is to be built, I would expect that fake-055 building to be modified first.