He will be via flashbacks, the same way Kazumi's playable in T7 despite her being dead for 20+ years prior to T7's story.
Free Step Dodge
ChaolanLegacy
UpSideDownGRUNT
Mishima's never stay dead he'll be back for sure, Kazuya "died" by volcano in Tekken 2 yet here he is in Tekken 4-7 lol they'll retcon his death or make up something.