A brand new trailer has been released for Tekken 7 and it showcases a new addition to the Japanese arcade version of the game. In the trailer, Akuma from Street Fighter is showcased as a character, suggesting that he will soon be added to the Tekken 7 roster. Whilst this trailer is aimed for those who play the Japanese arcade version, it's likely that Akuma will come to Tekken 7 once the game gets a worldwide console release.
It's very common for fighting games to include guest characters from other games, TV shows or movies so seeing Akuma in Tekken 7 would be awesome. Akuma should have a move set that is very similar to his move set in the Street Fighter franchise so when you're playing him, it really "feels" like you're playing the real Akuma. Interestingly, even though Akuma is coming to Tekken 7, he has not been announced for Street Fighter V.
Akuma will be added to the next Japanese arcade Tekken 7 update, which has been named Fated Retribution. On top of the inclusion of Akuma, the update will add some graphical improvements and some other currently unannounced content.
So far Tekken 7 only has a planned release date for PlayStation 4 in Japan. Release dates for other consoles and regions have not yet been revealed by Tekken's publisher and so far there's no solid confirmation that it will even come to other countries at all. We'd expect that Tekken 7 would most likely make it to other regions at some point following the Japanese release.