The limited attempts applies only to the following bosses: Professor Putricide, Blood Queen Lana’thel, Sindragosa, and the Lich King.
The limited attempts are shared between these bosses, so if there are 15 attempts total and your group wipes 5 times on Professor Putricide, you will only have 10 attempts for the remaining encounters.
The limited attempts has increased this week to 15 and will increase to 20 when the Frostwing Hall opens and more will be added in the weeks following that.
As far as the release of the Frostwing Halls... we'll see soon enough.