I have now heard from both Xi Yazhou (some weeks ago) and
(this week, in discussion about the J-10D rumours) that there are discussions floating around of China providing J-10 to the DPRK to modernise their air force.
In context of J-10D Shilao and Ayi's opinion is that:
Yes, with only one engine it's cheaper than J-16, but it's not exactly half the price since it's not like J-16 is loaded with two AESA. PLAAF love J-16 and given choice would just buy more J-16 instead of more J-10.
J-10's small size leaves very little room for further improvements. If it has to be done you'll probably see things like conformal fuel tanks just like on some of the later F-16s.
If indeed there is to be a J-10D then perhaps it would be designed as a last batch of "perfected J-10", half for export to Pakistan/DPRK and half for PLAAF, but it's not very likely.