The expansion will be max level, so you will need to level up before going there. There is no indication whatsoever that there will be any changes to the new player experience with the expansion. Worth noting that you will get a free level max item you can use to get to level and enjoy the expac D1.
Guild Wars 2: Secrets of the Obscure™, our new expansion, begins on August 22. As part of today’s announcement, we’ve got an official page with a high-level view of the expansion as a whole plus deep dives into combat system changes, story, and instanced content.
XP earned by max level characters will go towards filling your current region's selected Mastery line, or into a pool which rewards you with 1 Spirit Shard every 254,000 XP earned. Before the May 24, 2022 update the rewarded equipment items were non-salvageable, but could be used in the Mystic Forge though.tpoANL.