Could the Fantasy Inklings (i.e. the Notion Club) have solved Tolkien's flat earth problem, and initiated the Fifth Age of the world?

In what is perhaps my most ambitious (and speculative) Tolkien essay thus far - I begin with Tolkien's 'flat earth problem', and end with a vision of the future of modern Man; via an imagined (but unlikely) collaboration of JRRT with fellow Inkling, Owen Barfield.