What if the legion and ina planned a combined offensive in late 43? With the bengal famine discontent might spread.
The Indian Legion was part of the German military, so they would be too busy in Europe to even be relevant here. The INA was likewise part of the Japanese army, so it would really depend on Japan's ability to invade India (which of course wasn't very successful in real life).
For Britain to lose control of India, I think that a fairly large segment of the British Indian Army would have to mutiny and defect to Japan, followed by various ethnic/religious nationalist insurgencies forming. The resulting conflict would probably be UK and loyal Indians, vs. Japan and Indian collaborators, vs. rival factions that would likely fight amongst themselves as well (Hindu/Muslim/Sikh/Buddhist/Christian/etc.)
Regardless of who wins WW2 in Asia, India would probably be partitioned/balkanized into even more smaller countries than it was in real life.