People had the exact same concerns when digital image manipulation software became popular, including the "we will never be able to trust an image again" question.
To answer your question, I think the biggest step we took in adapting to the ever-present risk that an image may have been manipulated is acknowledging that it's possible. As soon as people knew that something could be faked, they realized that having a purported photograph wasn't irrefutable proof that it happened and learned to ask for corroboration before making assumptions.
I think we'll learn to deal with this new development too.
To answer your question, I think the biggest step we took in adapting to the ever-present risk that an image may have been manipulated is acknowledging that it's possible. As soon as people knew that something could be faked, they realized that having a purported photograph wasn't irrefutable proof that it happened and learned to ask for corroboration before making assumptions.
I think we'll learn to deal with this new development too.