It has been rumored that several wrestlers from New Japan Pro Wrestling are making their way over to WWE. Odds are that most of them will join the NXT roster, rather than the main roster but AJ Styles may be a different case. AJ Styles was one of the only reasons to ever watch TNA while he was a part of the promotion and I've always thought it would be awesome to see him join the WWE.
The fear myself and many have with the wrestlers coming over from NJPW is that the WWE won't use them correctly. Whether right or wrong, many wrestling fans feel like the WWE can't build new stars. Names like Dolph Ziggler come to mind when fans think that the WWE is wasting their own talent. Hopefully that doesn't happen with the wrestlers coming from NJPW and if there is a wrestler that would most likely join the main roster right away, it would be AJ Styles.
The WWE plans ahead and John Cena and AJ Styles didn't just randomly post pictures of each other on social media. WWE.com has even published a story about this on their website, hinting that this may be something that will be revisit when AJ Styles makes his debut and John Cena returns from injury.