I only can see two countries in the region could "compete" somewhat with PLAN, SK and Japan ... for the rest countries in the region? they simply couldn't afford it ... the choice for them is either embrace China or closer to the US or perhaps both (like Singapore)
I don't want to get into too detailed of a comparison, but alone, I do not think the JMSDF or ROKN can match the displacement of modern surface combatants the Chinese Navy will probably be able to have in service by 2020, given the announced procurements that the Japanese and South Koreans have both stated for the next few years, alongside what we currently project for the Chinese. Even lumping the displacements of modern surface combatants of both JMSDF and ROKN together may not quite match the kind of displacement that the Chinese will be pumping out by that time.
Of course, it'll take the Chinese Navy a number of years to fully be comfortable with operating their new vessels in a fully capable way given the dramatic nature of this modernization and expansion, and all sides will have very capable SSK fleets and what not... but purely in terms of the displacement of modern surface combatants, I think by 2020 a clear margin of difference will begin to exist and may grow significantly bigger once we fully enter the 2020s, if the Chinese Navy really does intend to build a full 24 052Ds as well as a successor to 054A that may be produced in large numbers, and possibly even 24 055s as some rumours have said... assuming no dramatic conflict or significant economic slowdown occurs.