Since Oblivion, we have not really seen Radiant AI improve or evolve in any meaningful way. NPCs are still largely static, being bound by their schedules and being at certain places during the day. Beyond that and perhaps some lines of dialogue, most NPCs have little point or purpose.
Enemy AI are incredibly stupid, especially when you kill a fellow enemy NPC and they act as if nothing happened (happens in Skyrim all the time). If BGS isn't making any massive improvements to Radiant AI in Fallout 4, they definitely need to do it for TES VI. Low level enemies, for example a raider, should never even attack a Brotherhood Paladin clad in power armor. They should actively try and clear the area so that he/she cannot kill them.
As it stands, the only time an enemy will flee is when they are low on health and they will move a short distance and then duck hoping for mercy. Radiant AI needs to be smarter than this. I'd also like to see more tactics and team work employed by enemies. If the player were to go running and gunning into a raider fort, I'd like to see the enemies take up fortifications, try to flank the player, even use the environment against the player.
If enemies in Fallout 4 are nothing but cannon fodder like they've been in all the previous BGS games for quite some time, that will adversely impact the fun of combat. A couple of lines of dialogue and just aimlessly moving side to side while shooting isn't exactly what I'd call engaging or realistic.