Re: What will be the culture and language of the subcontinent after a century?
Yes, I agree with the main hypothesis that the language of Indian Subcontinent would be Urdu-Hindi with lot of English vocabulary. Probably, its geographical confines would extend to Indus in the West and Bangla Desh in the East. The culture would become homogeneous like in Euprope with regional pecularities retained.
It would be like Europe today is rather probably more homogeneous.
Pakistan is just a geographical name. It is not an identity based on culture. There are little chances for it to evolove as a separate culturo-civilizational entity. Over the time, Punjabis, Urdu-speaking Muhajirs, Siriakis, and other Indian people would relapse into the greater Indian sea.
The phenomenon is happening right now.
Other than language there is no part of culture, which is particular and differentiating to the South-Asian region anymore. Food, dress, music-genres, architecture, art etc. are (becoming) the same world over. The only reason we have linguistic similarities with north Indians is because the Sanskritic languages spoken in northern India have Pakistani roots (in the Vedic-Civilisation of Indus a.k.a. Ancient-Pakistan), thousands of years ago the north Indians discarded their own Dravidian languages and adopted the languages of the Indus (Ancient Pakistan) because they were conquered by Indusians (Ancient Pakistanis).
I disagree with you that everyone from Pak, India and Bangladesh will speak Urdu/Hindi… As much as Bollywood has done to promote a false pan-Indian image it still isn’t strong enough to change peoples languages, Bangladeshis have their own national language which is quite secure in their country, whilst it’s true that Hindi is the constitutional language of India most Indians can only speak English and their own state-language (Tamil, Telugu, Kannada, Malayalam etc.) which usually has nothing to do with Hindi/Urdu, the only South-Indians who can understand Urdu/Hindi are those that have lived in Hyderabad or Mumbai…
The River Indus wont be the boundary for Urdu/Hindi, the language is loved, understood and spoken as far as Afghanistan, I think in Afghanistan Dari (Afghan Persian) will be the sole language in the future but in all of Pakistan, including NWFP/Baluchistan (not just east of the River Indus) the language will be Urdu/Hindi it is inevitable with it being our national language…
Sanskritic languages of Pakistan/Indus are Indo-Aryan languages not Dravidian so as well as racial similarities (as DNA testing has shown) we also have linguistic similarities with other Central-Asians/Indo-Aryans (Persians/Iranians etc.)… The only reason we have linguistic similarities with Indians is because they adopted our Indusian (Pakistani) languages we didn’t adopt their Indian languages.
Other than language we also have religious similarities with other Central-Asians as we’ve adopted same/similar religion, our traditional clothing (which I believe should now be discarded for cosmopolite attire i.e. pant-shirt) is also Central-Asian with roots in Iran (Sherwani), Afghanistan (Shalwar-Kameez), Uzbekistan (Gharara)… Everything that has come to be associated with India is actually foreign (be it language from Pak or dress from Iran/Afghan). Whilst Pakistanis have claim to both Indo-Aryan (Vedic) and Dravidian (Mohenjodaro-Harrappa) heritage as we’re a mixture descended from both, Indians are mostly pure Dravidian (except for a few NW Indians) so they can only claim to only the Dravidian history of their own land (not of the Indus/Pakistan such as Mohenjodaro/Harrappa), their Indo-Aryan language and religion was adopted from us rather than inherited from forefathers.
Despite linguistic simialrities nobody will relapse into the "greater Indian sea", America and Canada have the same language and even the same race (which we don't with India) yet they maintain their individual identities..