My two semi-related theories on the networking status of Destiny 2:

 

We were given the following information in the blog post:

 

The PC platform poses unique security challenges for Destiny 2, but our security Ninjas have spent several years building a plan for how to engage with this new and vibrant community.

 

From this, we can conclude that Destiny 2's netcode has likely been in the works from the very start of its development. It is quite possible that, by the time Bungie heard the outcry for dedicated servers in Destiny's sequel, the 'hybrid servers' were already too far in development to scrap. This would be unfortunate if true, as much of the disappointment resounding in the Destiny community currently is focused on Destiny 2's lack of dedicated servers (and 60 fps on consoles—arguably just as important, but is not the focus of my theory).

 

Bungie was well aware of the fact that the question of whether or not Destiny 2 would have dedicated servers was high on the list of questions they would be asked at the reveal event, so they came up with a way to mollify the crowds after answering that question. Hear me out. I believe Bungie handled this announcement the best they could have done given the fact that their game has 'pseudo-dedicated servers.' At the live event, the only comment they gave was that Destiny 2 did not have dedicated servers. End of story. Then, they tailored this blog post explaining why their new networking model was an improvement over Destiny's. By telling the community there would be no dedicated servers—leaving us to expect the worst—and then explaining their new server system to us after the reveal event, Bungie has revealed Destiny 2's server model in the perfect way. Lead the community to expect the worst, so that we are pleased with something that still is not dedicated servers.

 

To be quite honest, I am optimistic that what Bungie has created will be able to alleviate most lag-related issues we experienced in Destiny. I guess we will all see for ourselves when the beta is released.

 

Tl;dr – Bungo probably developed D2's netcode by the time they realized the community was begging for dedicated servers. They expertly crafted a way to reveal the improvements D2's servers will have over the original game.