Stig and the team have said a couple of times during their interviews that it's not a short game. Ultimately, it's still in development so it's hard to put a number to it at this time.
On top of that, though, it's a Star Wars game, so it's pretty packed with lore and details that many are going to spend a lot of time checking out, discovering, and learning about, making it even harder to know how long an average playthrough is at this point (though, it's not necessarily a bad thing to have a lot to do and discover, haha).
For now, we're not going to share estimates on length, but know we're dedicated to providing you with something high-quality that's worth every dollar and hour you spend. Your time and money are valuable and something we respect. We have no desire to waste either.