
Eventhubs:
The version of Tekken 7 shown at the Japan Amusement Expo 2015 (JAEPO) will be the exact same build that is slated to go into service at select arcades all over Japan next week, according to reports from Japanese media from the event.
As fans have speculated with the listing of only 20 fighters on the "Characters" section of the official website, that is indeed the number of fighters the initial release version will come with. However, more fighters will be added into the game later either through time-release or other such mechanisms.

Katsuhiro Harada: "I’d like to share that I’ll be leaving Bandai Namco at the end of 2025. With the TEKKEN series reaching its 30th anniversary—an important milestone for a project I’ve devoted much of my life to—I felt this was the most fitting moment to bring one chapter to a close."

Gamereactor: "The Tekken series is celebrating its 30th anniversary, and to mark the occasion, veteran Tekken director Katsuhiro Harada - who has been involved with the series since the very first game - visited Sweden and we recently had the chance to talk to him."
I don't think there's been enough new characters between Tag 2 to now to warrant a Tag 3.
Besides, there's that other Tekken game supposedly not canceled.... TxSF......
Tekken tag tournament 2 is one of my favourite Tekken games ever so I would love another one :)

Trevor Walker said: Fighting games have always been able to simultaneously experiment and innovate while staying true to their roots in the best of ways. Mechanics change, crossovers take place, and evolution occurs. One of the best examples of all three can be seen in the coveted guest character.
However, more fighters will be added into the game later either through time-release or other such mechanisms. So.... microtransactions?
20 fighters? :/
i wanted to play as kazumi but hopfully her and the more fighters will be playalble in the console version