Those hoping for cross-platform play, akin to Street Fighter V, for Tekken 7 will be disappointed. On Twitter, the Australian branch of Bandai Namco confirmed it. You're stuck with people who also own the same system as you for competitive play.
Katsuhiro Harada, the producer of the Tekken series, also weighed in on the lack of the feature. He attributed it to a first-party issue, meaning the console gatekeepers. Despite the technical possibility, there are (allegedly) security concerns, which more specifically means, according to Harada, that a P2P connection across platforms contradicts internal security policies. Going from PC to either of the two console platforms would also “split” the PC version, which likely means there is some kind of technical limitation there with how Tekken 7 is built.
Cross-platform play is definitely in high demand. Despite the few games that have made it work, there are definitely hurdles, many of them likely corporate in nature. While we won't get to enjoy it in Tekken 7, maybe some other fighter will follow in Street Fighter V's footsteps and give us what we want.