There's just not the same precedent for it (YET!) on this level - the hard canon story arc level. Crystal Tower didn't literally bring us to Final Fantasy III. The Warring Triad literally didn't bring us to Final Fantasy VI.
This sums up what I think.
Crystal Tower and Warring Triad were fan service and well implemented in the game without linking 14 to other games.
It's just that, in regard to Ivalice, the amount of "fan service" and little things piles up a bit too much and it would really really feel odd that in the end there would be no connection.
I mean, they just need to reveal in a patch that the 12 gods from the Ancient times are "Hydealin ascien" to go even more in that direction and litterally make ff12 and 14 lore pratically the same... except for the geopolitical setting