I very seriously doubt this will ever happen, in light of the restrictions [1] Muhammad himself placed on the presence of non-Muslims in Arabia: "I will expel the Jews and Christians from the Arabian Peninsula and will not leave any but Muslim."

"Vatican plans to open church in Saudi Arabia," by Malcolm Moore in the [2] Telegraph (thanks to all who sent this in):

The Vatican is in negotiations with Saudi Arabia to open the first Catholic church in the kingdom.

Archbishop Mounged El-Hachem, the papal envoy to Kuwait, Qatar, Bahrain, Yemen and the United Arab Emirates said talks had started a few weeks ago, in the wake of King Abdullah’s visit to Pope Benedict last November.

Currently, all Saudi citizens are required by law to be Muslim, and the Mutaween, or religious police, strictly prohibits the public practice of non-Muslim religions.

The last Christian priest was expelled from the kingdom in 1985.

However, the Vatican’s relationship with the Muslim world is improving rapidly, and Qatar opened its first Catholic church on Sunday.

Mgr El-Hachem said a church in Saudi Arabia would be an important sign of “reciprocity” between the faiths....