According to me, it would be Australia vs SA/IND final at the Ovals, unless Sri lanks pull a rabbit out of the hat and clean sweep the Kiwis at the away tour, which seems unlikely to me.
But still, India needs to win a minimum of 5 matches out of 6 (which looks achievable). If they manage to win all 6 matches then they are directly going into finals and we'll have new WTC champions Australia lol.
All of India's matches are scheduled to be hosted in the sub-continent. They have two test matches to be played in Bangladesh and another 4 to be played in India (against Australia). It is possible to win 4-5 matches out of 6, but I am not certain at this point. For the test series between India and Australia, the latter will be having a major handicap because they don't have a quality spinner. Nathan Lyon doesn't look like he can trouble the Indian batsmen. Zampa is not that suitable for test cricket. Then there are emerging spinners such as Mitchell Swepson and Arjun Nair, but they are too inexperienced to be included for such an important tour.
Historically Leg spinners hardly make any dent against the Indian team. Late great Shane Warne is a fine example, he was a mighty leggie against all teams but whenever he came to India he never did well against Sachin, Sehwag, Dravid, Ganguly and Laxman and leaked plenty of runs with very little success under his belt.
On the other hand off-spinners (Graeme Swann) and part-timers (Clark) did well in India so Nathon Lyon would be okay. Ashwin surely going to outbowl him similar to the last Indian tour of Australia but the former should be fine on patches. Australia's best bet would be Nathan Lyon leading the spin attack with a couple of part-timers, maybe they should add Maxwell along with Swepson instead of Zampa.
One thing is sure, BGT is going to be very competitive and spectators are in for a treat.