Ferrari aren't remotely close to Mercedes on pace, I think this race proves that. Rosberg and Vettel on a two stop, Merc cruising, Vettel clearly being pushed to go faster by Hamilton yet still no where near Rosberg. They were 5-10 seconds slower per stint easily. Both engine saving for Merc tactical reasons and the early season more power focused races on a car that mostly improved in downforce rather than downright speed meant Merc didn't look as fast as they really are.
Australia suggested the pace difference but new car, massively changed engine, new driver and Vettel got 'stuck' behind Massa(or Bottas, forget which) left a small question mark about how much they would improve with experience and how much they were held up. Answer is not much to both. Merc appeared to be cruising in China and Bahrain, winning as slowly as possible being the saying banded around. There is a reason for that, Merc trying to save engine life.
Season could be interesting, tactical reasons mean Ferrari are closer than they should have been and got a win they didn't expect. IF, and it's a big if, Ferrari's engine upgrades bring bigger performance gains than Mercedes, then the rest of the season may be closer as well. However, it looks like Ferrari will either have to use the older engine spec at points later in the season or take an engine penalty at one race.