Worth is something only YOU can determine.
If you wait for the next best thing, you will wait forever.
Do not expect a bargain from the next series of top graphics cards. They will sell for a high premium, at least initially if they are much stronger than the GTX1080ti.
You must ask if your needs warrant a stronger card.
I would not consider a GTX1080ti or even a titan X to be a really big jump in capability over a GTX1080.
OTOH, if you are able to make the swap at a reasonable price, and you have the budget, I say go ahead and do so.
If you do not, you will forever wonder if you should have.
I have never regretted paying top dollar for the best.