In Yoshida's last letter, he mentions that a page detailing companies will be up on the Lodestone "shortly." That was five days ago. My question then: How long is shortly? How long SHOULD 'shortly' be? What is the maximum amount of time that can pass before something no longer arrives in a shortly manner?
He's either going to say a timeline that may not hold or he will not say anything at all. That's as simple as it is.

He says "Info on companies will arrive just before 1.17 goes live. 1.17 has been delayed by a week or two, and was supposed to be implemented by the end of March."

Should the players be given reading comprehension lectures?

Read the context and it's always pretty self-explanatory.