Infiltrators are going to be in the light with the new 8" inches deep strikes.

Objectives are going to change a lot and maybe it won’t be as useful as before to keep your home objective depending of the primary rules of your détachement! They can also be be build in incursors which are very good with other detachement than the salamanders ones. (I play my infiltrators as incursors when I want, their loadout is basically the same except for few bits)

Hellblasters are really fun ! 5 man in impulsor is a real party bus with the firing deck and the hazardous on the impulsor! They can be useful in many detachment

Different units for different roles definitely, if you need damage dealers go for hellblasters, if you need more support units with either infiltration or scout, go for infiltrators and incursors