Naruto and the QQ about the Doujutsu that is almost 100% foreshadowed.
Kishi has done nothing but foreshadow that Naruto is going to be the new Sage of the Sixth Paths, to assume he wouldn't be is ridiclious. How else do you think this will go? like really? Kurama even called Naruto Rikuden when he used his seal and shut down the nine tails after seperating his charka from him. Naruto's Nine Tailed Charka mode showed very good likely hood to the Sage's Symbol's, as well as BM mode is only furthering this point. Naruto is the jinchuriki of the Nine Tails, the tailed beast that is considered the strongest, AND the one with the most vile charka. A jinchuriki of the other tailed beasts in my opinion would most likely not transform their jinchuriki in the way that Kurama's Charka has to Naruto, it only makes sense that the one that has tamed the Nine Tails and has completed a full sync with it would become the new Sage.
There was one very convincing thread that the Senju Clan, and uchiha clan deprived from the Uzumaki Clan, therefore Kishi has had in mind that Naruto would be the new Sage of the Sixth Paths from the very start if it does turn out the Sage is from the Uzumaki Clan, and they are the parental clan of the Senju and Uchiha.
Kurama would be the hardest, and the most difficult to master as his Charka is literally hatred itself it seems. However, it would appear that the Sage of the Sixth Paths did not want his Sons to be his successor as a whole, he wanted a child of prophecy to more then likely become the nine tails jinchuriki, even 6 of the tailed beasts were like, YUP THIS IS THE ONE. Which would mean what exactly? They gave him some of their Charka, why? So the full transformation could complete, The Rinnegan at the moment would only be able to be activated by "apparently" Uchiha and Senju blood and dna, this is actually very unlikely as Madara is the only one who has activated the Rinnegan from the EMS, Madara hasn't explained, or flashbacked on how exactly he accomplished the awakening of his Rinnegan, but it seems that it would make sense that it takes a little bit more then just the DNA.
At the moment Naruto has quite the phyiscal strength, which would symbolize the Sage's Body with the Yang charka of Kurama, when the Sage used the Creation of All Things, why couldn't he put part of himself, or at least a little nudge for whoever tamed the Nine Tails and the Nine Tails accepted that they could develop the Sage's powers, with the Yin Charka naruto's Jutsu will become more powerful in full, this would be the FULL nine tails, the nine tails that is so powerful that naruto could run by tailed beast bombs of Six other Tailed beasts and deflect them. The Nine Tails being the strongest would carry the Sage's Will, or the Sage's Will of Fire literally, The Yin Charka, even though much would deny this, will cause Naruto to activate the full on SOP6 Transformation, Naruto is an Uzumaki, Naruto is accepted by the other tailed beasts, Kurama even thinks Naruto reminds him of the Rikuden, and well quite frankly it is stubborn to assume Kishi doesn't love Doujutsu and can't wait to draw his little knucklehead become the Sage of the Sixth Paths, we don't even know what he offical looks like, for all we know it could literally look exactly like Naruto with Red Hair, because it seems that's the Uzumaki trait, is dat red hair.
Moving on to Minato's Gift, OH SURE, Minato could give naruto the FTG, but how would that impact the fight anymore then his speed already? Madara and Obito know how Minato's FTG works, some would say Naruto would be too OP, however how can you even debate this, Kishi doesn't care, Naruto goes nine tails form anytime he was in danger, he had a life saver from the very start, it was all just development up to this point for the nine tails to accept him. The Yin Charka makes the most sense, Minato may of never assumed he could of gave it to Naruto again, but he sure as hell wasn't expecting the RDS to be removed and the whole 4 Hokage to be Edo Tensai'd. The gift, quite frankly, could be mutiple things, Naruto's Dad isn't just going to give him one thing in my opinion, it would seem that Naruto would get perhaps the Yin charka, an uzumaki scroll containing the secrets of the clan for sealing tailed beasts, + other sealing Jutsu's, Naruto excels at them that is. However, Naruto will get the Rinnegan, its only foreshadowed a little too much.