Short of the announcement of the World of Warcraft: Shadowlands expansion itself, one major reveal for Shadowlands is going to change things in the MMO forever. Blizzard confirmed during its Shadowlands panel at BlizzCon 2019 that the expansion will introduce World of Warcraft's first official level squish. In effect, that means that 60 of World of Warcraft's levels are being erased from the game, so as to create a much faster and healthier leveling experience.
The level squish, which will be introduced at the start of Shadowlands, will shrink to level cap down to 60. However, 10 of those levels will be reserved for Shadowlands itself. 50 will be where current max level players are brought to at the start of the expansion and they'll level to 60, 10 levels, just like prior expansions. So while the idea of a level squish may at first be intimidating, for regular players there won't actually be any meaningful difference to leveling in the new expansion beyond the change in number.
Where the changes will be noted is for new players and alts. The World of Warcraft level squish is entirely intended to make leveling a faster, easier, and more enjoyable experience for players. That's why new characters will now complete a brand new starting experience, leveling 1-10, and will fully level from 10 through 50 in a single expansion's worth of content. The example given is that at level 10, characters can choose to go to Pandaria and level all the way to 50 in just that expansion's content. At 50, Shadowlands' content will then be open for players to start on.
According to Blizzard, the new leveling experience is designed so that every single level that players gain will be rewarding. With each level, players will gain a new skill, talent, or access to an otherwise limited feature. It won't be quite the same as, say, leveling 1-60 like in World of Warcraft Classic, but it will streamline leveling so that players can get into new content as fast as possible. And they'll hopefully have fun along the way.
The reception to the decision has been largely positive. There are few World of Warcraft players who would tout the current leveling system, which requires players play through near every expansion, as efficient or fun. However, there is some controversy, as World of Warcraft players are familiar with Blizzard course-correcting in the past, often resulting in less expansion content overall. World of Warcraft players say they'd like an expansion to not have to fix such major issues and wish Blizzard would fix things outside of retail releases. Regardless, improvements are improvements.
World of Warcraft is available now on PC. The Shadowlands expansion has no current release window.