Nikki Bella Not Back Together with John Cena, Despite Thanksgiving Post

Nikki Bella is NOT reuniting or reconciling when it comes to John Cena ... and there's a perfectly logical reason she posted a romantic pic of them, making fans think they're tapping in on their relationship.

Sources close to Nikki tell TMZ ... the WWE superstars are still very much single, despite Nikki posting a shot of her and John cuddling in a hot tub at sunset.

We're told Nikki was simply reminiscing over the past year and thinking back on what she was thankful for -- she posted several pics of other people in her life -- and John was a part of that. Even though they called off their relationship and stopped talking to each other.

Haters will say she was trolling ... but we're told it was just some Thanksgiving reflection.

And yeah, sounds like the sun really has set on their romance. At least they'll always have #TBT if you're jonesin' to see 'em together again.