I never had any faith in Kejriwal or AAP, it is a party of activists who disrupts everything in India, and Kejriwal is an opportunist who made his political career by riding on Anna wave.
And yes, if not Modi, then Rahul Gandhi has the highest chance!!
Other strong contenders would be either of Mulayam or Mayavati from UP, Jayalalitha or Karunanidhi from South, or maybe Mamata also, all are real gems. All 5 are power hungry and won't allow a Third Front / Federal Front without getting the PM post, If not Modi, then we are heading for a really brilliant future.