First, prices usually never come down, considering next quarter end is coming and dollar will dry up in market pushing the price of dollar up again.
Second, I highly doubt new taxes will be imposed mid year and there is no rumor in market even, whoever told you that must have his/her motivation to lie.
Altis 1.6 is a good car and value for money.
If you browse the market you can buy 1.6 Altis with (27.56lac invoice) at 29-30 lac easily. Brand new zero meter.
Best time to buy anything is "Present"/"Now" always... since we cant make purchases in past and future is most uncertain in Pakistan.