The thing is that I'm not expecting a perfect product out of Fallout 4. Bethesda have never been remotely capable of that, but it'll be good enough for me to enjoy it, to feel as if it was definitely worth it. Why? Because I enjoy the series, I don't expect it to be the best game ever made, I don't expect it to work properly on release* and I'm not expecting it to have some incredibly innovative feature that's never been seen in a game before. What I expect is a game set in a universe that I enjoy exploring with a storyline that I'll enjoy because it's happening in that universe, even if it's not always the main storyline, which lets be honest shouldn't entirely be how to judge a FO game. I enjoy the setting they've created and I'm willing to overlook some shortcomings and give Bethesda some leeway whenever they create something new in that universe for me, regardless of if it was a stupid 2D platformer.
This is entirely the reason I enjoy TES games, yes they're not perfect but I enjoy the setting and the lore, every little bit of it. That's where I find my enjoyment in the series and the same is probably true for most people.
*What I mean by that is that it'll work, unlike Battlefield, it'll just be a little unstable in certain areas and some things will need to be ironed out as they come up.