I'm one of the few people who enjoyed ACIII, but maybe it's because I came to the series late and played it before its predecessors. TBH I'm mixed on this. I liked the ship missions in ACIII and I'm guessing that they are acting on that in this, however I am skeptical of something being announced this early after ACIII came out. Almost like Call of Duty all over again.
That trailer does look somewhat promising though, I have to admit.