As I understand it Ancestry.com will be doing their own indexing and FamilySearch teamed with findmypast.com and Archives.com will be doing their own indexing.
The difference is that in 2013 Ancestry.com will put their index behind their pay wall, and the index by Familysearch and their associates will remain free (like all records) on FamilySearch.
I for one intend to arbitrate and index like a freak when it becomes available.
I was attending a webiner the other day by Thomas MacEntee about how to use the various search tools to find your people in the 1940 census without the index, but think about this: if you used that time to index instead, how quickly would we all be able to find everyone we are looking for. I personally intend to spend no time trying to find people without the index, and will spend my time working on the index.
You can sign up to index at https://the1940census.com