In the meantime, I just found this size comparison of the KJ-500, KJ-600 and KJ-2000 respectively when viewed from space. Can't say it's exact, but pretty close in accuracy:
Notice the visibly larger radome on the KJ-2000 compared to the radome on the KJ-500.
Then take a look at this photo again:
Given that in terms of overall size, the newer radome to the right is almost similar to the radome in the middle (which is purported to be for the KJ-3000), and given that the radome to the left is similar to (if not basically the same as) the one currently used onboard the KJ-500 - Again, like what
@THX 1138 just said - The newer radome to the right is more likelier than not meant for the KJ-3000 as well as an alternate design to the large radome in the middle.
In the meantime, speaking of this older, smaller radome to the right side in the previous photo:
If the supposed KJ-700 project really does exist - Perhaps they've shelved it?
I do find it kinda unlikely that a Y-9-sized airlifter is capable of carrying such a large radome that was meant for a Il-76-sized airlifter without undergoing major modifications and compromises that follow...
Besides, even if the larger radome to the right is indeed meant for the KJ-700, then why bother with the KJ-3000 using a similarly overall-sized radome but with smaller radar arrays than the former?
Or was I thinking too much here?