One question from a neutral viewpoint(Please don't look at my flag)
From POV of china, Pakistan was supposed to be the first customer of J10B. If PAF chooses not to go for it, it would hamper chinese plans for J10B export. Replacing J10B with JF17s won't be enough compensation for them as JF17 is not used by PLAF, and hence export of JF17 is less important for brand building of chinese aircraft as compared to J10B.
Given that don't you think China will actively try to stop pakistan from cancelling J10B orders, which can result in using stick and carrot tactics forcing pakistan to accept J10B?
I believe it was Pakistan which had shown interest in J-10 and no the other way around, so don't think they will be forcing us to buy it. Had that been the case they would have not gone with us with the JF-17 and rather from the start pushed us to buy the J-10. As per insider details the Chinese are offering the J-10B to Pakistan at something close to 40M$, which is not we are ready to buy at. Had they wanted us to buy, they would have offered it at a lower cost so that J-10B has chances of success as an export product.
As far as my analysis goes and by looking at the joint Chinese-Pak marketing collaboration with respect to FC-1 / JF-17, they know that for the Chinese to make J-10B an export success would be very difficult as of now as its an expensive aircraft and as of now and in foreseeable future there is no one who would like to have J-10B especially when there is American, French, Swiss, European fighter aircraft programs. When J-10B becomes a true class fighter with its own engine, it will have to fight its competitors and the buyers would be rich ones and not the low or middle income level buyers those who don't have funds to buy a 40-50M$ fighter jet.
That is where JF-17 will come with a 20-25M$ price tag for buyers who wish to replace their old Mig-21s, F-5s, Mirage kind of fighter jets, with something which is 4th gen atleast. And that is where Chinese will win with hundreds of sale orders and keeping those countries on its side.
FC-1/JF-17 targets those countries who can not go for a 40-50M$ jet, but can buy a 15-25M$ price tag jet.
J-10B with PAF buying or not, will be opted by those countries who can buy pricey jets. But for that to have its own mature jet engine is very necessary.
Also, there is no clear indication that CAF (PLAAF) has not decided to induct FC-1. FC-1 prototype getting tested with Chinese weapon systems on the same airfield where J-20 & J-10B are being tested gives some other indication.