Mutable Realms president tells fan sites that subscription-base projections resulted in Wish cancellation:
The letter/e-mail states: “Wish has been shut down because with the data we gathered during the first 10 days of our Beta 2.0 test, even with our best-case projections for player numbers, we could not have reached enough subscribers for Wish to sustain itself."
GamerZone has the entire article.