I think the only thing that really has killed me so far as being true to the halo series is that the Covenant ships i've seen in this recent trailer look NOTHING like the other covenant ships.

 The whole "X" shaped rear section is just not covenant, at all.  They have that smooth, whale/waterdrop streamlined shape.  they don't have big rectangular sections. 

 There are a few other small details, but i find them acceptable.   Personally, i don't take these trailers so seriously though. I mean, they totally lack grunts and the other species, only showing elites, which makes no sense to me. 

THey are just trying to look cool.  Hopefully, when Halo Wars ships, we won't have to many things that don't fit Halo's styling.