If you try to level a new WoW character, you're basically asking for mad deja vu. Ahead of the release of a new expansion, Blizzard is gonna let players change things up. A lot.
During the World of Warcraft "What's Next" panel at BlizzCon, game director Ion Hazzikostas announced that level scaling - which was introduced as part of Legion and changes the stats/difficulty of enemies in zones based on your current level - will soon be expanded across the entire game. This means you'll be able to choose the order you advance through zones and take on quests from the get-go.
However, you can't, say, rush straight to Northrend and give Arthas a wedgie. Some zones will still have upper and lower limits, so as to retain a sense of progression. As an example, Hazzikostas said lower level Alliance zone Westfall scales from 10 to 40, while mid-level zone Burning Steppes scales between 40 and 60. He added that expansion content, once only doable in a set-in-stone order, will now present branching paths with both Outland (Burning Crusade) and Northrend (Wrath of the Lich King) scaling between 60 and 80.
According to Hazzikostas, game-wide level-scaling isn't that far out. Blizzard will begin implementing it as part of patch 7.3.5, which will be on WoW's PTR in "a few weeks".