I have not followed data much on Ys Online since it was blocked from people outside of Japan to know if it was still functional, but the email does not seem to imply that it will be transfering. They only speak of Shin Sangoku Musou Online. But if it is functional and you still have an account and somehow still play, and the transfer is going through- you will want to have your account transferred to Weeple.
I’m unable to research any further information because the Weeple website is not functional as of this time. I’ll try in the morning and see about editing the post if I can find out anything more.