As noted, rumors started today on WWE Universal Champion Brock Lesnar planning a return to UFC this year. The @TalkMMA page reported that Lesnar and Paul Heyman talked with top UFC officials during International Fight Week earlier this month, possibly for a fight at the November 4th UFC show from Madison Square Garden. It was also reported that Lesnar is now back in the testing pool for the US Anti-Doping Agency (USADA).
Other parts of the original story was denied to Dave Meltzer of F4Wonline.com, including Heyman being at UFC HQ with Lesnar. UFC sources did confirm that there is interest in having Lesnar fight again, if he wants to. Lesnar adding himself back into the USADA testing pool shows that he has at least some interest in returning to the Octagon.
Regarding Lesnar's status with WWE, Lesnar's contract is set to expire not long after WrestleMania 34 in 2018 and Pro Wrestling Sheet reports that he's already made it clear to WWE officials that he currently does not plan on re-signing. PWS adds that Lesnar has re-entered the USADA testing pool so he can make the right decision about his career once his WWE contract is up - return to MMA or re-sign with WWE.