There are Ahadith which are being used by extremist groups propagating a war against India. All these ahadith refer to troops going from Palestine and Syria and returning to those regions. Even if these ahadith were authentic, and they are indeed found in reliable books, even though I haven't investigated the respective authenticity of them, they have nothing to do with any possibility of an Indo-Pak war.
The other important thing to note is that Abu Huraira, the companion-narrator is suggesting that it was something that was about to happen during his lifetime. It is quite likely that Muhammad Bin Qasim's conquest of Sind was being prophesied in these ahadith. There used to be kings in India then; there aren't any kings there anymore.
The third important matter to note is that a message as important as the one mentioned in these narratives is described in all different versions of it through only one companion. Clearly, if the message was important, there should have been several narrators mentioning it.
This message therefore cannot be employed as an excuse to fight against India. We can fight against India or any other nation only if conditions of Jihad are satisfied, which are: it should be declared by a Muslim ruler, Muslims should be at least half as militarily strong as their enemies, and the enemy should be guilty of blatant injustice against a group of people. Any individual or group of people cannot declare Jihad privately on their own against anyone; if they do, they will be guilty of creating fasaad fil 'ard (mischief on earth).
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