How can trailing and forward P/E ratio of main stock markets show such huge difference
Am I right concluding that:

Stock markets are probably over-evaluated, considering the earnings in 2016?
Stock markets are over-optimistic regarding the earnings in 2017?


No, you cannot draw that conclusion a priori. You can conclude that the market expects a big increase in profits in 2017. You can have an opinion about whether the market is over-optimistic, but unless you got divine insight, or have better models than they do, you cannot conclude that their forecast is wrong. Remember that the market is a collection of people with access to roughly the same information that you have access to.