I have looked at the vistas and maps of the 2 current map-packs and I think that 343 could very well have put vehicle/concept art from Halo 5 in them.
The Hornet on Skyline and the evacuation going on in the background of Landfall.
There are other things that I have noticed, that aren’t so obvious, but the Hornet and the evacuation are the biggest things I have noticed so far.
If this is true, I think we will see more in the Castle map-pack.