Maybe I’m cynical but I feel that part of the reason they have gone with a multiverve type story is so they can leave open the potential for sequels in the future.
I think it's unlikely as Kitase, Nomura, Nojima, Toriyama and plenty more of the old guard will be retired within the next 10 years. A will many of our fav big name Japanese devs since the 90s and 00s.
I don't think FF7 has the mileage anymore for another cycle which is understandable considering it released 30 years ago and the amount of tie ins and reimaginings it's had and now 3 AAA remakes.
I think after the final game is announced we'll just get:
*Trilogy pack
*PS6 or PS7 trilogy upgrades or remaster maybe with edits and gameplay ehancements
*Maybe 1-2 DLCs
*Continued world orchestra's given how popular and timeless the music is
*Merchandise stuff
They'll keep it simple and low risk.
S-E needs to focus on bringing the main series back into the mainstream with either 17 or a reboot, releasing a new NieR, DQ, seeing if KH has a future with 4, thinking about keeping FF14 relevant and the next MMORPG and also some new IPs or revisitng old dormant ones.