Unless he has a late instinct to do otherwise Dhoni will almost certainly go in with five bowlers against Australia and that seems the most logical way of going about it. I suspect the recent behaviour of the Premadasa pitch might tempt him, the affair with bounce and carry on the track might have been no more than a mere flirtation, and in any case he has been happiest manipulating slower bowlers.
I wonder though if India will rush in with three spinners and a few others, who can answer to that call sometimes or whether the third seamer might just be considered. There is a case for that, with Yuvraj looking like he can contribute, but I'm fairly certain (as certain as anyone can be, for Dhoni holds his cards close to his chest) three spinners will be the preferred option.
It means one batsman has to miss out and the choice of bowlers might well determine who that is. If three seamers play, then Yuvraj must, but if only two are needed and there are enough slow bowling options, Dhoni can cast the net wider. I suspect it will all come down to the confidence with Virender Sehwag at the top of the order. A side that bats deep (Pathan, Ashwin, Harbhajan and Chawla at 7, 8, 9 and 10) can afford a Sehwag playing his usual way, but it is also true that in recent times he hasn't always delivered.