Idk, it seems telling to me that since Oda highlighted Akainu and Blackbeard together post TS in chalpter 650 (the chalter is literally about them) they may actually go down together before the WG itself.
Im not sure where Shanks falls into this. Maybe together with the rest, or maybe before by Blackbeard or after at Laugh Tale or the WG, but I do think these 2 specifically likely will fall together in a larger conflict than your standard arc. Just a feeling I have on that.