If "desta" means "from this," why does this sentence not mean, "From now on/(from this time on), we go by boat"?
It is an example of a particular usage of "desta vez". Actually it means "this time". From now on = de agora em diante.
Is there a difference between "desta vez" and "esta vez?"
Interesting. Thank you!
Can you say esta vez?
Is it really incorrect to use shall in place of will here? I know that not all languages make the distinction.
It is correct but is considered rather formal these days; it is probably used more in Britain than the US.