http://www.belkin.com/us/pressreleases/8798223729724
If priced similarly to the WeMo switch pluggable device, it could be an interesting contender. Would be nice to have a dimmer option though. Existing WeMo devices have been controlled via various 3rd party tools.
Update:
http://techcrunch.com/2013/01/06/belkin-wemo-light-switch-looks-and-feels-like-a-light-switch-but-with-wi-fi-control-for-50/

Update:
a Belkin representative told me it will hit store shelves this summer and retail for $49.95.
http://techcrunch.com/2013/01/06/belkin-wemo-light-switch-looks-and-feels-like-a-light-switch-but-with-wi-fi-control-for-50/