Serena could win 18 to 20 slams
Call me crazy but I still think Serena can reach 18-20 slams. First off it isnt untypical of players to be in their primes into their 30s. Navratilova was still in her prime aged 30-32, she just didnt win many slams and wasnt #1 anymore since the greatest ever Steffi Graf was also reaching her prime and was superior to her. Evert likewise played arguably her best ever tennis in her early 30s, taking her game to a new level to counter Navratlova, she just was overtaken by two superior player in Navratilova and Graf. Laver completed the Grand Slam at age 31 and his best years of tennis were generally to be believed aged 28-33. Court was still dominating at 31 and probably could have another couple years if she didnt take another pregnancy break. Agassi played his best ever tennis aged 29-33.
So I believe Serena, given good health, could play as well as ever these next 3 years, or atleast as well as any period outside her 2002-July 2003 where she hit an out of orbit level for female tennis. And unlike the others there is not an even greater player to overtake her while still in her prime, atleast not yet.
So 6 or 7 slams in the 2012-2014 period is very possible. Starting in 2015 she would likely start to really regress with age, and the field will have to have improved by then.