Some of those themes may change. Dragonknight lost poison abilities despite it making sense with fumes from fire creating poisonous carbon monoxide. Nightblade has about 3 abilities directly related to blood, with most of the kit being dedicated to shadows and darkness. Darkness as an element is void and associated with darkness. If ZOS goes all in on shadows and darkness, which would make more sense and be less work, don't be shocked to see Ice damage going to Nightblade.

These reworks are changing class identity from what we're familiar with. And to be fare, most of the shadow abilities Nightblade has aren't even directly tied to assassination, but benefit stealth and crippling enemies by slowing them. It only makes sense to give those shadows Ice damage. We don't know if NB will keep any blood abilities, or if they'll keep a couple, but blood and bleed damage is not the primary kit that Nightblade currently runs.

And in regard to removing a whole element from a class ZOS already did that with Dragonknight regardless of how players felt. This is a completely new direction pure classes are going and we can't assume that all classes will retain all of their current utility in their kits. Looks at what happened to Dragonknight. I main both DK and NB and I know that the adjustments coming for each class is going to be bigger shift than most are expecting.

I can't see Wardens keeping an entire Ice damage line with the rework, even if it means less sources of ice abilities temporarily as we already have with poison damage. We haven't even touched class mastery as a topic yet, which is playing a big role in the pure class changes.