well, there are many plots that kishimoto can still use...
obito is not yet the full bijuu, its missing 2 of the strongest tailed beasts.
naruto can hit him already.
there was no mention if the kyubi chakra can hit him or not.
it still possible that the fourth will transfer the dark kyubi to naruto before he gets released.
then naruto will have lots and lots of more chackra to share with everyone.
also if the kyubi stays as 2 entities inside naruto one can spare him sage chakra and the another kyubis chakra thus making a new eye that kyshimoto so much loves.
naruto can learn to transfer sage chakra to everyone and thus everyone will be able to hit obito.
hell if naruto gets both chakra types from the kyubi he can make a kyubi cloak as deference and sage chakra as offense