Capcom Unity announces that a "mix of paid and free DLC" will be released for the PC edition of Street Fighter X Tekken, saying this "should arrive by the end of the week." They also suggest that the next round of DLC for the PC edition of the brawler is probably coming around the end of September, saying:

Quick update for PC SFxT players - a big blast of DLC is on its way, and should arrive by the end of the week. As with the console versions, this batch is a mix of paid and free DLC... The full list is coming, but you can look forward to the replay analyzer, gem capacity expansion and extra colors, as well as a deluge of new gems and alternate costumes for all released characters.

Regarding other patches and the 12 additional DLC characters (which now arrive 7/31 on consoles), the timing has been roughly two months from console to PC. So, while I don't know the precise date for further updates, you can generally assume it'll be ~60 days after the consoles get it.

We're trying to shorten that gap as much as possible - apologies for the wait, guys. <3