The panel of Vikings did tell us
We are off to Paris, half way one of the main characters will die, there will be raids to other countries and yet again there will be bigger conflicts between characters.
The Paris attacks will continue if there is going to be a season 4 that is announced in the panel. Everyone thought at that moment season 4 was definitely a go, but they didn't hear it right. Everybody on twitter cheered that moment.
Also the rumours started who would be dead during the season. The trailer didn't give that information away. I do have a kind of opinion about this after seeing the trailer. I am not going to rumour about that.
"Bjorn will grow older, bigger and stronger". Alexander Ludwig who plays Bjorn told that.
The teaser trailer looks great and tells us a lot about the storyline of different characters. It tells us a strategy and what the seer sees for someone it is not clear who or what was asked. it gives you an idea of what it will be in season 3 instead of giving big storylines away. Go and see the teaser trailer for yourself.