A future FFG will be a blue water FFG that will fill in the escort role in blue water environment at far away waters like Indian Ocean and so it needs to be capable of long-to-mid range AAW as well as ASW. This means it needs to be larger, closer to 052D size.
I actually see a future FFG as being tailored for blue-water operations with Carrier Strike Groups in the Western Pacific around the 2nd Island Chain.
That is what I see the key mission as, and the current Type-054A propulsion setup looks too slow to keep with a Carrier
Remember Chinese ports and naval bases will likely be attacked, so where are those ships going to/from the Indian Ocean going to dock?
This means the follower up for the 052D will be a mid-size DDG--bigger than 052D but smaller than 055. 055 will be the capital ship, escorting and leading carriers, amphibious, and surface action fleet. While 05X DDG acts as the main workhorse, a role currently being filled by 052D.
This my vision of what I think PLAN is going for, but as always I could be wrong.
Yes, I think they will go with a larger mid-size DDG to replace the Type-052D for blue-water operations with Carriers
But if you want to discuss further, there's other threads