wanna ask, if my new iphone 6 is on 8.1 out of box, do i still need to do a full new restore first then jailbreak?

my baby is reaching in 2 days soon, i guess. and hopefully it is really on 8.1 out of box. somehow, apple still signing for 8.1 currently. if not, pray that apple still signing 8.1 when i get my phone.