Patch 5.0.4 will launch Wednesday.
Talents: Everyone will have to set their talents, and the talent trees will be extremely different.
Glyphs: I have bought and learned all glyphs on all my alts. I’m not sure if it’s the recommended thing to do, but glyphs are changing, so there is a big chance you want to equip a glyph you don’t already know.
Dust of Disappearance: At level 85 you can use this to change talent points and glyphs. At level 90 there will be a new type of dust.
Currency: All Valor Points and Conquest Points will be changed to Justice and Honor Points. So don’t buy any epic gear for Justice or Honor Points Tuesday, as you can buy better gear Wednesday with the points.
Enchanters: DE your relics, they will be trash Wednesday.
Scribes (inscription): Last chance to trade down inks is Tuesday!
Account-wide achievements, companions and mounts will be active from Wednesday, as well as AOE looting.