Pakistan will be lucky to afford anything over 150 JF-17s and 36 J-10s. While we can say 36 J-10s was in the work since quite some time, it would be difficult to believe they would purchase 150 J-10s anytime quickly. It took China a decade to get to 200 J-10s after all. While current numbers may not be a measure of what the future holds, the Pakistanis will have issues in purchasing that many jets. I think the current J-10s cost $40Million a piece, just $10Million short of a Flanker. It is possible the Chinese J-11s are cheaper to manufacture than the J-10s.
I think the current plan is to get 80 teens, 36 J-10s, 50 JF-17 Block 1, 50 JF-17 Block 2s and 50 JF-17 Block 3s. Or 100 JF-17 Block 2s and a fresh order for 50-100 Block 3s. The JF-17 orders are big by itself.
While they will eventually have their upgraded teens and 36 J-10s by 2015, they are planning on Block 3 JF-17s after 2015 period. So, that pretty much takes care of their 4th gen plans until 2020. Maybe an additional order of 36 J-10s in the meantime while they wait for China to introduce a light or medium class fifth gen fighter for induction after 2020. We are still talking about 100-150 fighters every 5 years from 2010 to 2020, which is a big deal for PAF.
150 J-10s by that time period is simply stretching it. China has it's own needs without having to give away 72-96 fighters to PAF while they don't have any kind of superiority over SAF, JASDF and USN.