I've loved every Deus Ex, even invisible war (forgotten,hugely fun for me) and mankind divided,the traditional lull moments. I reckon we're due another solid gold effort.
Unfortunately, with the current form that games are taking, any solid gold game is going to be a bit of a departure from previous ones. I think we're going to be looking at stuff like real open would, non-instanced missions, like MGS V but far more concentrated in terms of the physical density of the world and mission content. And you know, hopefully less divisive.
In my mind all DE needs to do is run cleanly, have assloads of entourage and obviously heaps of alternate routes through thoughtful architecture, have the right aesthetic (a little more glam than Cyberpunk is looking like being) and have very solid missions. Having next gen reactive, AI directed interesting people populating the typically kind of hollow/cardboard cutout/old fashioned world would be nice. It would be nice if they could really take the plot right to the end game, really send you down a rabbit hole. The dream is we love it so much that we don't resent the shuddering sigh of exhaustion that accompanies our 200th hour of sneaking.
And I think they should go down the Skyrim route of having dozens of pre-crafted encounters, rather than random generation.