The only problem I see here is that the RCC can only excommunicate Catholics. How many Catholics are performing or having abortions?
I doubt excommunication would overly trouble them, as they've already tossed any vestiges of their Catholicism via their acts.
Unfortunately, a great number of Catholics and "Catholics" are having abortions. As for abortionists, I think there are few who assert that they are still Catholic. However, there are legions of Catholics who promote abortion politically or directly or indirectly support scientific research that creates and destroys human embryos.
Excommunication is more about the condition of the relationship between the faithful and God. It really doesn't matter whether the Church proclaims someone excommunicated or not. If they are, it's because of their actions, not the judgment of the Church. Same goes for saints. It's helpful for the Church to identify saints, so that the faithful can emulate them in their own lives, but there are countless saints uncanonized and in heaven...