Pros And Cons:
"One State, one language" is a universal feature of almost every State. Examine the constitution of Germany, France, Italy, England, and U.S.A. "One State, one language" is the rule.
Wherever there has been a departure from this rule there has been a danger to the State. The illustration of the mixed States are to be found in the old Austrian Empire and the old Turkish Empire. India cannot escape this fate if it continues to be a congery of mixed States.