Because turbine can do better, and we should ask for something better. Think extension of, not replay of.
There are quite a few threads, and comments within threads, championing epic shroud to make epic greensteel (Tier 4 or 5 or something that would justify grinding it for endgame). I'm not opposed to epic shroud/vale, nor Tier4+/whatever GS. But I would like us to consider setting our sights a bit higher than old content revamp.
Consider: We have beaten back a devil invasion in/under the marketplace, then in the vale, forcing them back to their home plane, then we took the fight to Shavarath itself. There we defeat the principle architects Horoth and Sulu. So... who is left? The rest of the devil council doesn't seem to want to have much to do with Eberron, at least in the near future based on their actions in ToD. Is there anyone of significance around who might still have a grudge? What about Harry? I recall leaving Harry in a state where he was just a fraction of his former self, and very, very unhappy. With Horoth and Sulu gone, he can only blame himself (not likely) and his very temporary PC allies for his humiliation on Shavarath. Yes, I think we will need to finish things with Harry. And repeating the 13th eclipse with inflated HP/saves and maybe an extra twist with the traps or timers isn't quite enough.
Let's suppose Harry retained some kind of link with Eberron and Lamannia through the power he absorbed in the eclipse. With the right rituals and arcane devices (new altars/crafting stations) he attempts to create a massive gateway for a final assault. The gateway begins to manifest in the shroud, so the PCs have to go back into the shroud. Gotta do three things:
1) Close the gateway between Eberron and Shavarath that is manifesting in the shroud. We can reuse one or two maps here from the old raid, but everything else is new. Defeat an appropriate challenge here, then just as the gateway is closing leap through because we have to...
2) Close another gateway between Shavarath and Lamannia through which Harry is drawing great amounts of power from the life energy of that plane. And no, I'm not envisioning a 999k hp portal beatdown. Something more interesting than that. Maybe something to do with windlasher gnolls, and preferrably not elder air elementals, or maybe something completely new. Then after completing that task...
3) Jump through the collasping Lamannia gateway and arrive in Shavarath where we can take down Harry and put a stop to the devil threat once and for all. Or at least for a while, until the next general decides to take over.
Extra random thoughts: guest appearance by "Professor" Tremas, newly promoted lieutenant, who is very happy to not be Sulu's plaything anymore? or maybe not... maybe a newly armored Bloodplate? Or any other loose end that might need to be tied up?
I really, really think part of endgame should be back on Shavarath, or something close to equivalent, with a very satisfying final takedown of our old pal Harry, with a twist or three. We've stood around him in a circle long enough - same for other raid bosses. If we absolutely had to involve the Realms, I suppose I could point out the link between Yugoloths and Myth Drannor, and pose the question of what might the Yugoloths do in response to a sudden power vacuum within the devil legions. Somehow I don't think they would completely approve of Celestial forces gaining a significant upperhand...
That, for what it's worth, is my 2cp for a "real" epic shroud and possible new endgame raid. YMMV, thank you, peace.