[Amarie of the Vanyar]

Has anyone else come across anything which might suggest that Sauron was in fact cast into the void upon the Ring's destruction?

Saucepan Man, there are at least two places in which this is suggested . The first one, when Gandalf talks to the Witch King in Minas Tirith:

'You cannot enter here,' said Gandalf, and the huge shadow halted. 'Go back to the abyss prepared for you! Go back! Fall into the nothingness that awaits you and your Master. Go!'

The Siege of Gondor; The Return of the King

And the second one, in the last words of the Valaquenta:

But in after years he (Sauron) 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

Of the Enemies; Valaquenta

The first quote suggests that the Witch King was also cast into the Void, after the destruction of the Ring