Isn't this a trick that will only work once? Wont the people who are taking advantage of black money start using a different store of value that isn't controlled by the Indian government like foreign currency or high value commodities?
But what this does is adds cost to doing business secretly in cash. Also it increases the threat of government taking another bold move in the future to flush out more stores of black money. Basically, it increases the risk of operating outside official accounting, making that option more scary and less appealing.
Watch for real estate crash in New Delhi. On paper there wont be a crash but sharp growth, because the declared transaction value is about 40% of the real transactions, the remaining being in cash. With this move, declared values will move up, while actual values will move down.
Also remember that Bitcoin isn't really anonymous and it's fully traceable. So the police merely has to do some rubber hose type de-anonymization of which Bitcoin address was the payment made to you in and from there on, all your transactions can be back-traced.
EDIT: fixed typo "tomorrows"