The plot above shows the % Urdu speakers vs. % Muslim in states where Muslims are 4% or more of the population. The data is from Census 2011 (thanks for Vikram of the language data). There are some interesting trends. Assuming that the vast majority of Urdu speakers are Muslim, it seems that in India the core Urdu-identified region is in the Deccan and to the east of its traditional heartland, in Bihar. In South India, 30% of Muslims in Tamil Nadu may be Urdu-speaking. But in Kerala the fraction is almost zero, while in Gujarat and West Bengal less than 10% of the Muslims are Urdu-speaking.
Below the fold is the table.