This was a no-brainer to have happened. As one of the parents of Vistara, Singapore Airlines was always going to use its own reach to allow for Vistara to gain traffic in India. And one of the tools for that is the frequent flyer program.
Just this morning the airlines (Singapore Airlines and Vistara) have announced that the flyers on both the airlines will be able to earn miles/points on taking flights on the other partner with effect from March 2015. For redemptions on the other partner, it will be possible from May 2015 onwards.
KrisFlyer members will be able to earn and burn for Vistara flights in the new partnership, and similarly Club Vistara members can earn and redeem points for travel on Singapore Airlines and SilkAir flights.
Of course, the earn and burn rates are not known yet, so it is a shot in the dark to figure out where to credit your miles. I’ll update you when I have more information.