Can we be given the option to continue to pay for our subscription in October?

[Bharata_Senka]

I am currently on track to receive legacy membership but only if I'm allowed to continue to pay for my account into October. However, according to the announcement, the game will be free to play as of September.

Nobody else seems to have noticed this yet, but your understanding of FTP in September is incorrect. November 1 will be the final save maintenance, with November 11 being when servers go down.

Legacy qualification = have paid for three consecutive months during 1.0 service

So long as you started your Sub by August 1, you should be in the clear. August, September, and October will qualify you for Legacy. If you started after August 1, you may be short by a few days depending on when the billing period ends.