I agree that Ise's next step of development is attain a sub-species of his Boosted Gear - which, will most likely be related with the Dividing Gear that he has stolen from Albion.
After all, Ise has already attained Balance Breaker of his "regular" Sekiryuutei powers - and I see no reason to change that, especially considering the fact that Ise's Trident and True Queen, can be... sort of, considered as the sub-species of his "regular" BG.
Regarding Ise's dragonifcation ability, I don't see much progress in that regard, until the situation with Ise's lifespan is going to be stabilized, in some way - after all, it's an ability that is related with Ise's "new body", which is still in a pretty unstable state, since the opposite elements of the "Infinite" and the "Dream", haven't reached a balanced state, yet - which, I think is going to be resolved in the end... since I doubt that Ophis or Great Red wanted Ise to have to undergo "medical treatment" for the rest of his life, when they have "created" Ise's current body for him...
And finally I could see, Ise developing a few more magical spells, considering that he has taken interest in it, during the events of volume 14 - it probably won't be something too complicated, since magic isn't Ise's "strong point", but I could see him, developing a spell or two, that would somehow, provide some variety to Ise's combat style, if he is... again, put into a situation, where he can't utilize his Boosted Gear's full potential...
And on a slightly different note, how do you think "Rias breast's" are going to be used, in order for Ise to awaken his dividing powers
