According to the Wrestling Observer membership site, current TNA star Sting may have "sent out feelers" to WWE.

This past Monday on WWE Raw, Sting was one of the high-profile champions featured in a series of video packages highlighting the history of the World Heavyweight Championship, which WWE portrays as having lineage back into the NWA and WCW days.  It's believed that by placing Sting in one of these videos, that casual and newer fans who might not be aware of Sting's legacy would be introduced to him in some small manner, should he ever make a play for WWE.

Sting's contract is currently on a year-to-year basis, and will come to an end at the end of the year, which will likely stir up more conversation - will he stay with TNA, retire, or sign to WWE, whom he has never wrestled for.

Last month, Sting spoke with VOC Nation Radio and told them "The year that they did the vignette (for Undertaker), I had nothing to do with it and I had no conversations with the WWE at that time. Shortly afterward there were conversations (with WWE) just by happenstance but nothing official.”

Sting also said "I’ve always wanted to wrestle Undertaker; I’ve said that for years.  And who would not want to work WrestleMania."

Source: PWTorch.com