I don't think you restart the atlas ever, it's just an additional new system on top of normal maps. The thing with the Atlas over current system is you can +5levels maps(so you could like +5 T14 and they'd be crazy xp, or you could +5 gorge and they'd be even better xp than currently, or you can +5 something else to be roughly at the equivalent of gorge, without actually being gorge) and you can add a bunch of mods to maps. They also said specific drops in specific areas of the atlas, although that's basically the same as divination cards dropping in certain maps. For the big boss I guess what happens is you need to find the maps for the 4 bosses everytime you want to kill him, so it takes a while, similar to Atziri. Can just buy maps too.
The new item types sound interesting though, and that minion damage helm looked pretty cool for summoners, but you still have to craft it after. Still nice. Combine with the new league minion speed mod on rings you can craft, and sounds like minion builds are gonna be a bunch better with the expansion.
Still need to see the new skills and I assume the balance changes. Sadly won't be for a little while I guess.
Edit: Detailed article:
Path of Exile: Atlas of Worlds Interview. A Map of Condensed Hype.
Notably stuff like "For each different type of map that you complete, you receive a cumulative 1% bonus to map drop rates. This encourages lateral exploration of the Atlas."
Also Chris explained more in detail how the +5 level works. You can only have 15maps total with it, and it can only be used to upgrade white maps to yellow and yellow to red(not red to +5). It is however permanent after you've done that, until I assume you use it on another(might need a regret orb or whatever to remove one).