It is too early to predict if Sheilla or Jaqueline will be able to maintain their level of performance in 4 years as well as it is too early to predict if Brazil's team will be a real candidate for winning gold in Rio de Janeiro OG.
Overall, all teams are getting better and better. In the mid-90s there were only a handful of teams which seemed to fight with Cuba for the most important titles: Russia, Brazil, USA, and China. All the other teams were in a lower level. Last decade Italy entered this top teams roster and other teams have improved a lot like Germany, Poland, Serbia, Turkey and Netherlands. In the last couple of years, Japan has also shown how good they are and we could watch the evolution of Thailand, the Dominican Republic and South Korea.
I really hope Brazil could maintain their level, and it is nice to see the renovation of the team won't be as traumatic this cycle was it was 4 years ago. Anyway, it is crystal clear to me that other teams will be as strong or even stronger than Brazil and the pressure of winning the OG before their fans will be more like a threat than an advantage to Brazil's NT (The 2007 Pan-Am Games are a proof of what I am claiming).
I also think Zé Roberto was lucky in London and his criteria for picking the 12 players for these OG were really questionable to say the least. We have a good team and so have other NTs.
USA, Russia, Serbia, Italy, Germany, Poland, Turkey, Japan, China and South Korea also have excellent players and can beat Brazil. If all Brazilian players could play in high-level, if we don't have injury problems and if our coach makes the right decisions, then we are one of the candidates, but it is just impossible to say if there is or not a favourite for winning the 2016 OG right now. Lots of things will happen until 2016.