Where exactly are you looking? I don't see the 4th-gen Touches listed ANYWHERE on Walmart.com.
Walmart, AFAICT, has totally botched their handling of the 4th-gen Touch. As you say, initially Walmart.com offered it for pre-order. But it said it was for Site-to-Store only. Okay, no biggie, so I try adding it to my shopping cart to checkout, and it won't let me check out because even though the product is marked as Site-to-Store only, it won't let me select Site-to-Store...it's not even an option! If I select my home address, I get an error telling me that I can't do that. @#$%!#^#% !!! (Both the Walmart.com support staff as well as the local Walmart employees were completely unsympathetic.)
The following weekend (Labor-day weekend), all references to the 4th-gen Touches were removed from the site, and to this day I still cannot find it mentioned anywhere. Searching for iPod Touch does not bring them up. Searching by Apple model # (for example, MC544LL is the 32GB model #) used to bring up the pre-order items, and now I get 0 search results.
So, again...where are you seeing this on Walmart.com? What do I need to be searching for that I'm apparently not?
Thanks,
-- Nathan