Three factors are going to be detrimental for the current political set up:
i) The Military-Zardari Tussle. Unless one is able to tame the other, the political situation will remain highly volatile. Zardari is of course banking on the US support (financial and moral) at the moment. However, historically, the US has found it more efficient and pragmatic to deal directly with the military establishment (because the establishment can act decisively independent of mass pressures and because it is the key power in Pakistan, which wouldn't let itself and its apparatus (ISI) be undermined by a civilian government);
ii) The US 'War on Terror'. The American 'War on Terror' is highly unpopular in Pakistan and Afghanistan. Zardari is increasingly seen by the masses as a lackey of the US who has replaced General Musharraf. His recent declaration of Kashmiri insurgents as terrorists is a political blunder not only for him but also for Pakistan. That is definitely not something that would help his already checkered image with the masses. Some even say that he has probably signed on his death warrant with that statement;
iii) The Economic Crisis. With real reserves (after accounting for future liabilities) estimated to be only $3 billion - enough to afford about one month of imports like oil and food - Pakistan's economy is close to bankruptcy. The poor and working classes were already suffering for a long time, now the middle classes are also finding it difficult to make the ends meet. Local newspapers are increasingly citing incidents where individuals sell their organs or commit suicide because of hunger and poverty. In the worst scenario, there could be food riots and a breakdown of the state. A logical political consequence would a military take over.
A challenging time is ahead for Pakistan if the downward spiral of ongoing political and economic crises continues.