Re: Urdu as our national langauge
The notification bringing Sindhi under Eighth Schedule says that:
There have been persistent demands from the Sindhi-speaking people for the inclusion of the Sindhi language in the Eighth Schedule to the Constitution. ** Although at present Sindhi is not a regional language in a well-defined area, it used to be the language of a province of the undivided India and, but for partition, would have continued to be so.* The Commissioner for Linguistic Minorities has also recommended the inclusion of Sindhi in the Eighth Schedule to the Constitution. On 4th November, 1966, it was announced that Government had decided to include the Sindhi language in the Eighth Schedule to the Constitution. The Bill seeks to give effect to this decision.*
So, if there was some population of Balochi, Saraiki, may be they had a chance in India to get their languages scheduled.
As far as Indian Sindhis are concerned, they are minority but influential one. A little that I know about movement for getting recognised Sindhi as national language, Sindhi writers like Mohan Kalpana, Popti Hirananadani and others actively pursued the case.
A detailed account of the struggle and reasons for getting Sindhi recognised as scheduled language is provided in the link below.