If a baby had never seen someone walk before, would it learn to walk? Can anyone make any assumptions on this?
I’d have to guess yes. Kids learn other things, such crawling, climbing up onto a chair, climbing trees later on, etc without necessarily seeing it done by others.
Our three kids all learned to solve toy problems (such as putting proper shaped blocks into same shaped openings) without any help from us when they were in the 1-3 year ages.
They learned how to get into all sorts of trouble without ever seeing us do the same. 
Also, people who are blind from birth seem to do okay.
This reminded me of the “Wolf Girls” of Midnapore, who were literally raised by wolves. Though one learned to walk bipedally once under human care (the other died), they had not learned to do so with the wolves. Instead, they walked on four limbs.
http://www.feralchildren.com/en/showchild.php?ch=kamala
It’s interesting stuff.
The Master Speaks: Has a human child ever been raised by wolves or other animals? Cecil indicates that most feral children walk on all fours.
True, but their parents/siblings walk upright, and a blind child would presumably notice that, by sound and feel, let alone the encouragement from the parents to walk upright (e.g. - holding the child’s hands up and letting them get the idea of walking upright with that support).