Mehrans will probably continue for some time, unless there is eminent chance of some Chinese company setting up plant in Pakistan and introducing a low cost model.
Looking at those sales, I think Suzuki will be more troubled with introducing something instead of Liana - which has been a total failure. Problem here will be, Liana is performing poorly so needs to be replaced. But on the other hand, if they replace it soon, then it puts a dent on their reliability as people would be speculating the new replacement wont last long either-- thus effecting sales, as people will be apprehensive of availability of spares as well as resale. What they did with Baleno is still hurting them.
A new improved shape of Liana (a little longer and a bit wider) should be top priority from Suzuki's PoV.
The other car is, of course, Alto, which some have already suggested is getting a newer model.