This is my opinion, please do not be offended by it.
This is what I believe the map of Tamriel will look like in the time following Skyrim.
Here's my prediction, I know it looks a bit odd, but here's what I see happening. The Empire crushes the Stormcloak rebellion and gains full control of all of Cyrodiil, Skyrim, and High Rock. With this, the empire decides to target the redguards for access to more land, and islands to prepare for a future Aldmeri invasion. During the war, the Altmeri Dominion joins in on the Empires side. Hammerfell crushes the Empire at High Rock, then makes the province a vassal state to help support them in the ongoing war. Hammerfell takes control of all the islands between it, and the Summerset Isles, crushes the Altmeri Dominion in naval, and land combat, then takes Valenwood and Auridon from the Altmeri Dominion. Without the connection to Elsweyr through Valenwood, Elsweyr defects, and is vassalized by the Empire.
If you have predictions of how Tamriel will look in the future, please use the map below.
Here's a map of what it looks like during Skyrim if anyone joining in needs a reference point.
[EDITED] I think it's really hard for Argonia to conquer and keep the control of Morrowind, since, first of all, they don't seem to want it, and Morrowind wouldn't be taken by the Argonians. If it was, I dare to say that the Argonians could only do so with the frontier territories.
But, as I mentioned earlier, they don't want to do it, after all, they already had their revenge... Which was repelled by the Redoran army.
It's been quite some time since the eruption, and Morrowind's reconstruction already began. Also, there were cities that were spared from the eruption, but attacked by the Argonians...
My point is that it is liveable (even Vvardenfell), and in some decades, it will return to it's former glory, as stated by Neloth.
The Dunmers wouldn't be ignorant enough to provoke the Argonians in it's weakest state. They're not Nords. And even if they can't enslave Argonians anymore, there's always those cats. I'm sure the Argonians wouldn't argue about that... Maybe even form a partnership, although it's highly unlikely. However, they wouldn't interfere for sure.
Also, I forgot to mention earlier, that Morrowind now is filled with Heart Stones, which true potentials remain unknown to us, and I'm sure the eruption revealed quite a few things...
I too think the empire will be gone (or nearly gone) by ES 6. I agree with 'The Dominion" control. I agree partially with the Argonian control, but I think it will be the Black Marsh and only the southern region of Morrowind; the Dunmer will regain control of the northern half of Morrowind (mainly because the Argonians will make no effort to hold it - but will continue 'raids'). Hammerfell, High Rock, and Skyrim will all be independent but have some type of mutual defense alliance. Some of the other borders may shift around (such as Skyrim may expand east and south, Argonians may expand west, the Dunmer may by further north, and some parts (SW portion of the grey area) of Morrowind will be under Dominion control.
Just my thoughts if the Stormclock victory is canon. With the loss of Skyrim, the Empire would effectively crumble, giving the Dominion the chance to advance. High Rock and Hammerfell form an alliance to prepare for the imminent invasion, but Ulfric refuses to enter Skyrim into the agreement. The dominion quickly takes Black Marsh, leading to a mass exodus of Argonian refugees into southern Morrowind.
I just don't see Black Marsh getting taken. If it falls, it would mean no more Argonians (since they would not have access to the Hist). I think the remainder of your map is plausible. I think the Stormcloaks winning the civil war will be canon, but Ulfric will die the same year as their victory (and it'll be sketchy whether he died before or after the stormcloak victory). With Ulfric dead, a new leader may be more open to treaty negotiations with Hammerfell and High Rock.