I've finally decided to settle on Nikon's D7000 -- and it's got me thinking now.... most every camera nowadays uses some variant of the Secure Digital format, be it full sized SD cards in the DSLRs, down to microSD cards in cell phone cameras. SD's versatility and ability to transcend form factors has served it well, in addition to being much easier to insert and handle (in comparison to e.g. CompactFlash and SmartMedia), and being relatively cheap per unit of storage.
About the only other format I see any of is the MemoryStick format, and I think that's more because Sony wants to prop up their proprietary format by incorporating it into their consumer electronics, not because the industry as a whole really enjoys using the format.
However, this has only been the case for the last ~5 years. SD is older than this, but it seems CompactFlash used to be the only thing you'd see in high end cameras. My guess is that for a long time you could not get SD cards nearly as large as CF cards, but nowadays that's not the case, so people have migrated to the much more people friendly SD format. (I still have nightmares about shoving in CF cards and bending pins on things....)
Anyway, SD seems king for now just as CF did a few years ago. Are there major changes anticipated in "digital film" anytime soon that may displace SD?