I watched a video of Warframe's alpha gameplay and was startled that I had to think of 1999. I think this is intentional.
My speculation would be that DE were thinking of how different today's gameplay is from the original one, that both have their own merits, but there is no way to bring back the original gameplay without completely throwing the last X years (hyper fast movement, room nuke, power fantasy) out of the window. The two systems are just not compatible anymore. And they don't need to be, if they stand side by side.
Given that there's already coexistent ways to play the game, see Duviri, adding "Retro Warframe mode" in parallel isn't far fetched. Only to give it a lore-coherent way to exist, they went beyond turning the dial back just in terms of gameplay, instead shifting the setting. What that might mean for 1999 is that it'll be their attempt for more tactical, slower combat. The kind of pacing one might see or remember in early game footage. I would speculate on conventional mission types like exterminate and defense and so on, just draped in the 1999 style. And I'm completely fine with that idea.
