We can't really have a single format. MicroSD, SD, and CF form factors each have places where they're appropriate. CF is needed for pro cameras which need many gigabytes of storage which would be too expensive in an SD form factor. Likewise, MicroSD is needed for some devices too small to support the SD form factor. On could of course substitute Memory Stick or xD for SD, if one wanted to be a market-contrarian.

My point is that there is a place for more than one format. The current set is way too big, yes, but there's little or no reason why we can't just all settle on one of the existing ones. A new format will be just that - a new format - until every device currently out there using CF, SD, and so on is replaced. So why make things worse when we don't have to?