I don't think it will be possible to max out a character without grinding long after all the game's content has been exhausted. Of course, one doesn't have to actually max out a character to reach a point where he's overpowered relative to the environment. I never came close to maxing a character in Skyrim because the game only scaled to 50th level and by the mid 40s my character was getting too powerful to be enjoyable to play.
The Fallout 4 system as presented can work quite well, depending on how quickly you level. If leveling is too fast the game can get out of hand but controlling the leveling rate will be possible with even the most simple of mods, which console users will be able to use this time around. It will be an extremely simple matter to slow down the experience gain rate to a point where you can complete the game without even coming close to having a maxed out or even over-powered character.
One way or another, MY game will scale just fine. I'm not worried.