Sim, ele provavelmente estava condenando o Rei Bruxo ao Vazio. ponte dos vilões do Senhor dos Anéis acaba indo para lá. Como você diz, o Silmarillion confirma que Sauron acabou no Vazio:
"Sauron had a part, and was only less evil than his master in that for long he served another and not himself. But in after years he rose like a shadow of Morgoth and a ghost of his malice, and walked behind him on the same ruinous path down into the Void.”
(Silmarillion)
Provavelmente isso ocorreu com a intervenção dos Valar:
The realm of Sauron is ended!’ said Gandalf. The Ring-bearer has fulfilled his Quest.’ And as the Captains gazed south to the Land of Mordor, it seemed to them that, black against the pall of cloud, there rose a huge shape of shadow, impenetrable, lightning-crowned, filling all the sky. Enormous it reared above the world, and stretched out towards them a vast threatening hand, terrible but impotent: for even as it leaned over them, a great wind took it, and it was all blown away, and passed; and then a hush fell.
(Retorno do Rei
Nossa dica é o "grande vento", que claramente pretende fornecer uma associação com Manwe.
Algo muito semelhante aconteceu com Saruman:
To the dismay of those that stood by, about the body of Saruman a grey mist gathered, and rising slowly to a great height like smoke from a fire, as a pale shrouded figure it loomed over the Hill. For a moment it wavered, looking to the West; but out of the West came a cold wind, and it bent away, and with a sigh dissolved into nothing.
(Retorno do Rei)
Tom Bombadil enviou o Barrow-wight para o Vazio:
Tom stooped, removed his hat, and came into the dark chamber, singing:
Get out, you old Wight! Vanish in the sunlight!
Shrivel like the cold mist, like the winds go wailing,
Out into the barren lands far beyond the mountains!
Come never here again! Leave your barrow empty!
Lost and forgotten be, darker than the darkness,
Where gates stand for ever shut, till the world is mended.
At these words there was a cry and part of the inner end of the chamber fell in with a crash. Then there was a long trailing shriek, fading away into an unguessable distance; and after that silence.
(Irmandade do Anel)
Mas isso não deveria nos surpreender. Provavelmente, todos Homens vão para o Vazio. Até Gandalf fez, na forma mortal.
Then darkness took me, and I strayed out of thought and time, and I wandered far on roads that I will not tell.
(As duas torres)
O dom dos homens é precisamente que eles são não ligado ao mundo.
It is one with this gift of freedom that the children of Men dwell only a short space in the world alive, and are not bound to it, and depart soon whither the Elves know not
(Silmarillion)
Dito isto, há outras coisas in o Vazio além do Vazio: os Salões do Illuvatar não são um lugar ruim.