I'm hopeful and even a bit excited about this. I don't think they need to do much to make it replayable. When I got my box set in the 80s, I kept running games through the Caves of Chaos, thinking that was the game. Then I started making my own dungeons on graph paper. Then I discovered modules in Walden Books, attracted by I6 (Ravenloft) cover and my mind was blown.
I feel that none of the starter sets for 5e came anywhere near to capturing the magic of the first starter set for younger players. Something a non-gaming parent, aunt, uncle, or grandparent can buy at target and you can replay with your friends instead of a one and done adventure. Phandelver was great for existing players looking to ease into the new rules and maybe older kids. But it had little stand alone, replayability potential. It wasn't great for getting younger players into the game unless they had parents or older siblings already into the game.
When I was looking into getting my kids in gaming, the best product by far was No Thank You, Evil! The production quality was good. The rules were accessible enough that non-gamer parents could play it with their kids. And it had younger player friendly components but still was fun to play if you were older.
It looks like WotC has learned some of these lessons. My main concern is how accessible the rules are going to be for younger players and non-gaming parents. 5e rules, while not terribly crunchy, can still be intimidating if they just throw a rules booklet at you. Presentation of the rules can make a huge difference in making them accessible. Put spell, power, and item rules on cards, have an intro scenario that takes you through social, exploration, and combat scenes, stepping you through the most common rules.
I don't want this to appeal to an old grognard like me. If my non-gaming sister could buy this at target and play the game with my niece and nephew, and replay it, then that would make it a good intro starter set.