First off, equipment rewards will be added to the Main Scenario quests. He didn’t go into too much detail here, but presumably this will help you reach the item level requirements for duties, if not bring you all the way there by itself.
Second, so that you can do the required content without getting stuck in queues for an eternity (especially for dps classes), players new to a given duty will be placed in a priority queue. Basically, you can go straight to the front of the line so you can progress your quests quickly.
Additionally, pre-50 main scenario quests will give double experience so you don’t have to do side content, and if you own Heavensward you’ll get experience from the 2.1-2.55 quests as well, so you can get a few levels before even entering Ishgard.
And if you have friends or a helpful FC, they’re adding the ability to join with a partial group, bypass the duty finder, and not get level synced. (This part is actually from other articles) With this, if you really want to skip ahead even with the inprovements, you can just have a level 60 player rush you through the old content quickly. There are plenty of great FC’s out there that would help with this.