In a recent interview with the U.K. based Digital Spy, TNA President Dixie Carter beat the competition drum really hard in regards to WWE and even went so far as to say she would do a crossover event featuring stars from both promotions.
From the article:
"I don't think [the WWE] shares my belief in this, but I believe that competition is 100% positively essential. I think it's important for fans and for us. To have one company dominate, a) it's boring, and b) you are not being challenged enough. It's always better to have other options out there and I truly believe it makes both companies better."
When asked if she would ever be open to the idea of WWE and TNA stars appearing together in shows, she said: "I absolutely would do that. I'm not sure if they would do that, but I absolutely would."
She may not be sure if "they" would do that but we can be reasonably certain "they" wouldn't. And that's because it makes absolutely no sense on any level for WWE to co-promote an event between the two companies.
Sure, you could find a die-hard fan of professional wrestling to fantasy book a show featuring stars from both sides that would make the hardcore audience salivate at the thought. But the reality of the situation is that WWE would be taking a major step down while TNA would be taking a major step up.
In other words, it's a one-sided deal. All gain and no loss for TNA, all loss and no gain for WWE.
So, yes, this isn't something that is likely ever going to happen. Feel free to fantasy book a card for it anyway.