Went to a couple Targets and a Walmart yesterday and today. As expected, found no series 3 but did learn a couple things.
At a Walmart near my house that I don't recall ever having any series 1 or 2, I did find a few 6-packs of series 2 with some cups showing Minute Mud and Ebayer. The checkouts at this store seem to have been totally overhauled in the last month or so. I'm assuming the series 2 cups have arrived within the last month. Even though there were very few traditional checkout lines, the 6-packs were in the area where the traditional checkout lanes had been pulled. Perhaps that is where we'll find series 3 when it shows up.
Today I ran into the Excel guy at my local Target. While he wasn't overly helpful, I was able to ask him enough questions to, well, learn very little. He said he knew nothing about any new Wacky Minis coming. He said he stocked all the Targets in my area, usually (always?) on Fridays, so it seems that may be the day to hit the ones near me at least.