Joe Belfiore has been teasing us this whole week with unreleased apps supposedly residing on his Windows Phone.

So far he has delivered the new Skype update, The Dark Knight Rising and Pandora, but in the tweet above he notes that his “week” runs from Monday to Monday, suggesting rather strongly that we can expect one more major app in two days time.

With Pandora already delivered and Instagram not even being rumoured, I think Viber, who has already confirmed the app is more or less ready, is the most likely candidate.

Do our readers agree? Let us know below.