In regards to unmasking the Breen and removing the mystery, I think back to the words of Spock: "After a time, you may find that having is not so pleasing a thing after all as wanting."
It could go either way. Someone around here postulated they were proto changlings. That's pretty interesting. There's other cool ways to spin it, and lame ways also of course. Like all this stuff, I think "Ok, now what?". I hope what they come up with outweighs the fun mystery of the Breen.
Personally, I think it's the best season so far, however the bar was not very high to start with. I wish Discovery started like this season, instead of the way it actually did.