Letter is likely a response to how poorly season ticket renewals have been going.
This.
The problem is that Eugene Melnyk can say all the right things at this point, but no one will believe him. His credibility is shot.
I think the Senators are embarking on a full rebuild, and this letter hints at it. I don't think they can reveal their "the plan", or really be straight forward about it right now because an integral part of "the plan" involves trading Erik Karlsson to kick start a rebuild. So they can't really reveal that until it happens.
People will say "but Dorion wanted to make a hockey trade" with Erik Karlsson. I think hockey trade is lingo for "give me a young player far enough along in their development that I know even if everybody else busts, I'll have something to show for Karlsson". It doesn't mean, give me players I can win the cup with next year. Dorion wants a Sergachev, or a Theodore, someone who is NHL ready and even if the 3-4 1st round pieces that he gets in a trade otherwise never pan out, he knows 5 years from now he'll have at least one player from the Karlsson trade playing a key role on the Senators.