Anand will have White in the morning, and will surely feel some urgency to make it count. In the past, almost all of their games - as with almost all of Anand's White games in general - have started with 1.e4, when the most common openings have been Najdorf Sicilians and Ruys with 3...Nf6 (not always reaching the Berlin Wall). Anand has done very well in any case - and is 2-0 against Topalov with 1.Nf3, too, but those games were played a long time ago.
My expectation is that Topalov with play a 3...Nf6 Ruy. Your guess?