The 787 is the 310 replacement for air India. We all are getting clouded by Australia,Japan and Europe but we need to realise the 787 market is also for the middle east, south east and particularly Saudi Arabia, which lies beyond the reach of the airbus 320 family and too near for the 777, along with hong kong. The Kerala to Saudi market is mostly Y. And hong kong is doing well on the 777 anyway. Singapore is another market where the 787 would replace the 320, and I think air India would be testing the waters initially with 18J and change configuration later on.

THe airlines seat configuration you are comparing, that ratio I doubt we will ever see with air India.

18 seats feel like a lot, then I realised its only 3 rows of J class.

The only problem with this is if air India uses 787 to replace the 777 routes , then that would be quite sad, because that is not what they originally bought them for. But then it's air India, any things possible.