There is > 100,000 MLC products rolling out into shipping devices now or soon depending upon vendor.
http://www.channelregister.co.uk/2009/10/19/microns_34nm_nand/
http://www.theregister.co.uk/2010/08/17/stec_mlc_sauce/
SLC has a problem coming in that flash is going to hit a geometry wall and better density is going to be bigger boost from layers rather than shrinkage.
Vendors are moving to push MLC into more "enterprise grade" contexts.
Howver, there are also SLCs now up in the 1,000,000 erase range too. (that gives you about 1,000 erases per day for about 3 years. )