Who said they ever plan on releasing kidvoker only immortals in the future? You're just assuming now. There is a bigger chance they release normal invoker immortal or maybe one that works with both. Or this year they might release kidvoker only item and next time they release one that works with both. Who knows, maybe they plan on making artistry work with kidvoker, but hasn't gotten to it because they wanted to focus on getting kidvoker released first.

We already got a taste of this in earthshaker new immortal. It works without Arcana, but it also adds a second style TOGETHER with the arcana too. and it will be sold on market next year, where people can't get the earthshaker arcana with it.