Southwest Airlines officially confirmed on Wednesday, December 15th, that they are converting 20 of their 737-7H4 orders to 737-8H4s. The upgrade to the -800 variant will allow Southwest to expand the range of their route network. All of the 737-8H4s will be ETOPS-capable. According to the Dallas-based airline, they are looking to purchase at least 70 737-8H4s by 2014. The first Southwest 737-8H4 is expected to be delivered in March 2012.
In local circles, this announcement has led to speculation that Southwest could expand to HNL, though they have not formally stated that HNL is new route, only a possibility.
Southwest's press release link.