My expectation is that D&D Encounters will have an adaptation of the first part of the Tyranny adventure - perhaps both adventures, but most likely only one, if the two link to each other to form a levels 1-15 campaign or similar.
You then have the option of continuing your character in either store- or home- play with the Tyranny adventure. In the Living Greyhawk and Living Forgotten Realms, these were called "adapted" adventures.
Stores and conventions, meanwhile, have access to additional adventures (of all levels), which can be used by brand-new characters, characters that have gone through Encounters, or characters who have gone through the full Tyranny adventures. These adventure may also be available for home groups - they were in both LFR and LG. The big question is how many of these adventures there will be...
The major difference in this programme compared to the old is that D&D Encounter characters were one-offs. Once the Encounter season ended, they could only be used in home games. With this one, once you've played through the Encounters, you can continue with the character in other Organised Play events.
Cheers!