I must be weird or something, because I don't see one-hour adventures as desirable in any way.
I really just think this is a wording issue - and I agree that they can come up with a better term for what they are hoping to achieve. But, as I understand it, what they mean by 'Adventure' is NOT a complete campaign or even, say, a complete old-school 'module' but a building block, a design concept, that includes the Three Pillars (Combats, Exploration, and (NPC) Interaction.)
So, if they get the ruleset tweaked right, it should be possible to complete a single Adventure Block in about an hour (grain of salt there). However, if you should like it to play slower for you and your group then that is fine also.
It's a design goal and a guideline but not the law as it were.
A single gaming session may consist of players running through two, three, or even four or five Adventure Blocks. Each built around consistent XP maximums available to be earned by the PC's and used as a (measurement of) difficulty level for the DM in the construction phase.
The underlying idea seeming to be whereas, with 4e, a single gaming session may have only consisted of one or two combat Encounters exclusively, a DNDN session will be built around including a little bit of everything, making for a more varied and fun gaming experience.
I'm a bit of a loss as to nomenclature at the moment. 'Encounter' primarily seems to be equated with combat as does 'Delve' conjure up Dungeon Crawling. 'Adventure' seems to be to all-encompasing as evidenced by the confusion in this thread.
I can well imagine blocking out the outline of a story with adventure hooks, making a map and seeding it with Adventure Modules chock full of Three Pillars goodness and letting the PC's roam the map freeform advancing from levels 1 to 5 in the process.
Will this be a 5e possibility? Here's hoping.
Dave