What you failed to mention SkySurfin was the rest of that press release.
United are closing down "Ted" their LCC, and are bringing all the A320s into Mainline United colours to replace those 737s you speak of, as they have identified a weakening in the low cost end of the market. Makes perfect sense really, especially if those Ted pilots are on a lower rate of pay (i.e. Jetstar v. Qantas).