In my view it depends on yet another question, what is the need of the hour?

Let us not forget there was a time when United Pakistan (East plus West wings) used to have only one national language despite the fact that there lied a thousand miles gap between the two wings. The fact that Pakistani leadership (which was based mostly in the West Pakistan) refused to give Bengali the title of national language (Bengalis were demanding that Bengali be considered national language along with Urdu) contributed a great deal towards the eventual separation of the two wings (note that Bengalis-speaking citizens outnumbered the rest of the Pakistani population). We must not forget that disaster and learn from that unfortunate event what we can do to keep the rest of the country intact.

In today's context, Urdu is not really a language that represents any particular province or region or city, but it is a language that is spoken in all the provinces of Pakistan (yes there is a minority called Urdu-speaking, or Muhajirs, who specifically speak Urdu but that is too small a population that they are not the main reason why Urdu is or should be our National language). There is no other language that is spoken in all the regions of Pakistan. So, in such a scenario only Urdu should be allowed to hold the title of National language as bringing any other regional or provincial language at par with Urdu at this moment will only trigger an unhealthy, detrimental competition between people who speak other languages. It will make matters worse for the country also because the four provinces already do not enjoy the level of unity that they should have among them.

However, it is not a bad idea to give languages facing the risk of extinction the status of ‘official languages’ (Pakistan already has English and Urdu as its official languages). As for the ‘national’ language Urdu should suffice.