I doubt they will be as strong as you think. I remember correctly they both lose their moon/sun powers. Tho these two would still be strongest in Narutoverse.
The mark was just for the seal. Aside from his TSB, COAT, and multiple chakra natures Naruto should be around the same capability wise well + the addition of another Kurama.
Sasuke on the other hand might have lost black chidori, but Sasuke doesn't have a range restriction on his S/T Jutsu anymore, and has probably beyond mastered the rinnegan.
I have a hard enough time thinking of ppl that can handle their chakra avatar alone :|