Some months ago, I had a hunch that Danzou might be Tobi.
With the latest issue, that hypothesis becomes clearer.
The part where Tobi said "I have another matter to attend to." He must be referring to the meet in Konoha, and his plan to proclaim himself Hokage.
Of course, I'm not 100% sure, but it's a wild guess. I still think Danzou is Tobi, concealing his right eye with the Eternal Mangekyou with that bondage.
...So what?
I mean really, asssuming Madara and Danzo are the same person(Which I doubt), Danzo could literally go into the men's restroom and into the stall taking a shit, finish, teleport to Tsunade, stab her in the head, and then exit the bathroom. Who would suspect him when he had an alibi of taking a shit when the murder took place?
my point is this: in the world of naruto, just because you can hear someone in the bathroom, see someone in the bathtoom, and even touch someone while they're in the bathrom, freshly pissing away in the urinal, doesn't actually mean they're there.
but lets step away from that for a moment. assuming that no one thinks to accuse danzo do you think the council is just going to lie down and take it? if modern day investigators were to go over this, regardless of whatever they found pointing in anyones direction they'd realize that a very probable motive for killing the hokage would be so that whoever becomes in charge would It have their rule interrupted, at which point danzo becomes a suspect regardless of his abilities and regardless of proof, and all hokage candidates becomes suspects. thus there is only one solution that the elders can come to if they have any sense. if the aim is to get tsunade out of the way so that the new hokage can be hokage forever, then the logical choice of action is to simply elect no one as hokage until the mystery is solved. that leaves danzo in the cold assed out. you might be thinking that a hokage has to be in power asap for the villages sake but thats wrong. when the third was killed the village took who knows how long to elect a new one.
first the council had to decide how to handle the immediate threat, that meant finding and curing the wounded, creating temporary shelter for people while more permanent houses were created, new building plans, treaties sighed with the sand and the sound, and other things that would require the resources of the council and village, then enough time went by for everyone who was hurt to heal (which could have taken days to over a week), at which naruto and jiraya went on their quest to find tsunade. we all know how casually jiraya takes everything, and we know that they ****ed off at plenty of inns and and the like on the way, and then they had the conflict with itachi and kisame after which point they probably had to lay low, point it took a long time for naruto and jriaya to travel across the land of fire before they finally found tsunade, at which point naruto took the week to learn rasengan.
so my point is that it may have taken weeks to months before a new hokage was elected. in a month many things could happen. sasuke could come some new enemy could come, the council could have more discussions and decide that danzo isnt actually fit to lead. a whole bunch of stuff could happen that could result in danzo never becoming kage, simply because he killed tsunade.
so it would be a very unwise thing to do. danzos current plant, that of using politics to become hokage, is his best bet.