No, that is not how this works.
Let's look at some facts:
Bangladesh is extremely poor, so there is more room for growth. Pakistan was where Bangladesh is today, about 10-15 years ago.
Now Back then, Pakistan didn't suffer from energy shortage much (natural gas or electricity)....however as the economy expanded and the demand for power grew, Pakistan choked on it's own. Pakistan's main hindrance to economy is energy only. Because there is tons of money in Pakistan that can be put in factories, but if you don't have energy, then those factories cannot do anything much. In every industry, Pakistan is still way ahead of Bangladesh.
Bangladesh Installed capacity of electricity is 11,500 MW which is derated to 10,500 (
http://www.bpdb.gov.bd/bpdb/index.php?option=com_content&view=article&id=150&Itemid=16|)
Pakistan's total installed capacity is well over 20,000MW, but as due to fuel mismanagement it produces 16-18000 MW.
Let's look at natural gas, Bangladesh demand is 2.5 billion cubic ft a day, Pakistan's is greater than 6 billion cubic ft. Our supply and demand gap is same as Bangladesh total demand
Now we have twice the installed electricity capacity as Bangaldesh and more than twice the natural gas demand....yet our population is 190 million and Bangladesh is 160 million.
So with just 18% more population, why is that Pakistan needs twice the energy amount?
As Bangladesh diversifies it's industry from textiles into other sectors, they'll realize that with energy shortage they too will stifle their growth. So Bangladesh cannot keep growing at 6-7%.
As with any developing economy, you have much room to grow in the beginning, but it will slow down after a certain amount of organic growth has been achieved.As there is the case in China is slowing down because they have expanded so much, but India can grow because they have much room to grow. India will find that after 10 years, they too will have to face the same. This is the process of any country going through a development phase.
So saying that in 12 years, Bangladesh will surpass Pakistan, is really not stating much. Not that it cannot, but my question is, where is that growth going to come from? And during that time, Pakistan won't be sitting still. As energy projects come online, economy will easily add 2-3% growth to the gdp rate.
I hope you understand.