Vegapunk states that mythical zoan DFs can be perfectly cloned. Something we've seen first hand with Momonosuke's dragon fruit.
Given that we know that the Gomu Gomu no mi is a zoan, something Saturn and the gorosei specifically know; I think that sometime during Egghead, Saturn will collect Luffy's blood and that from this, York will clone the gomu gomu no mi.
Who will eat these gomu gomu no mi clones? I see a few possibilities.
The first possibility is Blackbeard. Blackbeard is a D and Luffy's greatest rival. He also has 2 DFs, one logia and one paramecia. Teach stealing a gomu gomu no mi clone would fulfill his role as Luffy's greatest rival. Luffy has the nika fruit and is a joyboy. As a result, shouldn't his greatest rival also be a joyboy? By getting a gomu gomu no mi, Teach would be a second Joyboy. This would obscure Luffy's chosen one status and force the two to duel it out to see who will be the true joyboy of this generation.
I think a second possibility could be Vivi. She is a D and hence could serve as a second joyboy. Don't think this is very likely tho because I think Vivi will have the Nikyu Nikyu no mi, which is probably the fruit Lilly used to disperse the poneglyphs. Still, I see it as a viable option since she is a D and doesn't have a DF. If she ever gets captured by the WG and is sent to meet Imu in mariejois, I could see her stumbling upon the cloned gomu gomu no mi and eating it.
Lastly, I'd like to nominate Koby as a possible future user of this fruit. Koby is essentially the Luffy of the marines.
In his first major role post skip, we see him freeing slaves on Hachinosu. A trademark of Nika. With his similar fighting style to Luffy's, he'd no doubt make great use of the gomu gomu no mi were he to acquire it. One thing against Koby is the fact that he was portrayed to be a great swimmer. However, I could see him eating a DF in a desperate attempt to become stronger. Garp's capture by Teach could be that very thing. If he is going to face off against Kuzan in the future, I could see him utilizing G2 to counteract Kuzan's freezing powers. Given how strong Koby's base is, even simple gomu gomu no mi techniques like G2 or G3 would surely offer him a massive boost.
