The 2020 rotation and the arrival of the new Standard Year will, as always, be decisive in Hearthstone.
Three expansions will rotate out of Standard mode (Witchwood, Boomsday Project and Rastakhan's Rumble) and this should create a real revolution.
While they'll still be able for playing in Wild mode, a lot of Shaman cards from the previous expansions are going to leave the Standard mode, meaning that several different archetypes that are currently shaping the meta will be affected — or will even disappear.
Some of these cards weren't really used, but the disappearance from some others will definitely be noticed...
Witchwood
Boomsday Project
Rastakhan's Rumble
Just like the Pair Shaman with the departure of Genn Greymane, the removal from its core card will make the Shudderwock Shaman disappear.
The other versions of the deck will be able to continue to exist, notably the Galakrond Shaman who keeps all his "Galakrond pack". The Quest Shaman, much less present at the moment, could perhaps return in the spotlight, as long as the Lackeys are in Standard mode.
Finally, the departure of Thunderhead will definitely handicap the Overload/Aggro Shaman but thez archetype will remain strong as long as it can rely on the Doomhammer, Lava Burst, and Lightning Bolt as they belong the basic set of the game.