The supposed and rumored figure of 250 JF-17s and 150 or lets suppose 100 FC-20s give you the 350 figure, add to it the F-16s which we are gonna keep having and who knows how many more we may get in future, the figure stops at 90 or so, or it increases.
So i believe the PAF has already started its homework about increasing its strength and is looking at around 400+ combat strength by end of this decade.
i have serious doubts abt achieving 250 thunders until or unless there is a 'technological innovation' in the later blocks.
upto 2015 look for PAF to have
100 F-16s
150 Thunders
40 FC-20s
40 Mirage (Rose survivors)
40 F-7PGs
370-400 is the max range - beyond that $$$ restrictions will pre-emp any plans of expansion - expansion is also directly proportional to the health of the economy. if we r still fighting WoT in 2015, then forget expansion - remember the army gets the bulk of the defence budget (~40-45%) - the balance is split between the airforce and navy.
India always endeavours to hold a 3:1 superiority in numbers - its budget is 40-43 sqdns - twice the number!!!
in the 60s, 70s and 80s the PAF depended on 'force multiplyers'. can it revert to that 'advantage' it previously had - i am not sure, but this is the area it shd concentrate on - not sheer numbers!!!