Will the world being forced to a single religious & philosophical view result in a return to the Dark Ages?

It seems very doubtful that the world be forced into a single religion & philosophy in the forseeable future. We've got fundamentalist Islamist governments that benefit from remaining as such, fundamentalist Christian Russia, indigenous faiths in the PRC that the gov't will use to its own advantage, rising Hindu nationalism in India, and ideological freedom in the EU, Japan, and their former colonies -- which will reject all of those other faiths since they're not forced to adopt them and remain ideologically diverse.

With such wildly different religions, a single philosophy is very lunlikely to coalesce. I think we're safe in this regard.