The passive is the most likely thing to go or be changed.
It's NOT ABOUT STRENGTH,if it's about balance and a healthier gaming experience. The game isn't just balanced for you and the players playing Kalista,but also for the people facing her.Prior to rework Yorick and Poppy were kept weak or they would be balance nightmares-A RIOTer even mentioned if Poppy got play,she would be nerfed immediately.
Her E is highly likely to stay,because it's not a problematic ability,her passive on the other hand is another matter.
They're lots of thing they can do leave it on her,not just in it's current state.
Making it use an ammo system/max jumps over a duration/ a buff ability on Q/W lasting for X-period or something else.
The reasons why isn't picked is because she has been nerfed into an unpopular state cause of her passive.
If I'm not right why are they reworking her instead of just increasing her numbers? Simple balance changes won't fix the core issue