There is currently no legal issue blocking WWE from hiring former TNA talents. At this time, there has been no movement in the TNA vs. WWE lawsuit since former office worker Brian Wittenstein was hit with a permanent injunction preventing him from discussing or sharing what he knew about TNA confidential information back on August 20th.
There was a temporary injunction against WWE regarding the same material, but the court lifted that after the company had shown they their computer records and files did not contain any TNA information.
The bottom line is this; the case is still ongoing but there is nothing legally preventing WWE from hiring someone if they choose. It obviously wouldn't look good though.