Whether or not those sets will have precons is currently unknown, but we can hope
You should not expect to see this in any other formats, and its something the PFP [Pauper Format Panel] is specifically interested in and thinks Pauper can handle given the accessibility of building decks and the predominance of online play, PFP member and Magic principle game designer Gavin Verhey said in the accompanying blog post explaining the decision

Breath Weapon Choose Your Weapon Concealed Weapon Deathleaper, Terror Weapon Diamond Weapon Dwalin, Weaponmaster Dwarven Weaponsmith Efreet Weaponmaster Foam Weapon Kiosk Godo, Bandit Warlord Improvised Weaponry Iron Fist, Living Weapon Legacy Weapon Pact Weapon Renowned Weaponsmith Scavenged Weaponry Seasoned Weaponsmith (playtest) Tawnos's Weaponry The Immortal Weapons Thran Weaponry Toggo, Goblin Weaponsmith Ultima Weapon Viashino Weaponsmith Weapon Rack Weapon Surge Weaponcraft Enthusiast Weaponize the Monsters Weaponized Scrap (playtest) Weapons Manufacturing Weapons Trainer Weapons Vendor World Champion, Celestial Weapon X-23, Deadly Weapon
An effect that allows you to spend mana as though it were mana of any type to cast Imperiosaur won't allow you to spend mana from a source other than a basic land to cast it
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This type of play can be dangerous against many decks so beware of that tendency