GamesBeat: How long a game is this going to be?
Gustafsson: It's a bit weird, because this is our biggest game yet, but it's a pretty short production time. Like I said, the story is lighter in content as well as tone. But the level progression and the non-linear narrative gives us the ability to add a lot of activities and a lot of missions to do, so the total game time is actually longer than our previous titles. I think we're looking at at least 25 to 30 hours if you play through everything.
Also VG24/7 conducted a separate interview with Gustafsson where he revealed that Mecha Hitler won't show up in Wolfenstein: Youngblood as Hitler was killed by BJ before the events of the game
VG24/7: What was behind the decision to kill Hitler off-screen?
Gustafsson: We are actually pretty strict when it comes to following the lore and the storyline, and so obviously some of these things that we haven't really told in the main storyline, say, from New Order and New Colossus, those things have still happened,"
Gustafsson: We're actually explaining some of what has happened during these years, but we are still staying very true to the storyline. And I know it might sound a bit weird or even controversial that we're actually mentioning that in the game as well, that your father was killing Hitler, but that already happened in Wolfenstein 3D as well.
More at the links above.