The discount, which brings the iPhone 4 from $197 to $147, will be available through the end of June. Fortunately, the promotion applies to both the white and black iPhones, on both Verizon and AT&T. As usual, the $147 pricetag applies to eligible upgrades and new 2-year contracts.
There could be many reasons for the discount. For one thing, Walmart has been a strong partner with Apple since 2008, and their massive retail presence can offset the price drop. Also, Walmart is trying to increase consumer recognition of their dedicated wireless departments. And, while the 'select stores' haven't been announced, we imagine that any Walmart with a dedicated wireless department will feature the discount.
Unfortunately, Walmart's website offers no information on their available stock. So we suggest you don't wait until June 30th. Happy hunting!
source: Walmart via Apple Insider