As long as they remain profitable with their signature campaigns, there should be no signs of stopping anytime soon.
There are so many other reasons as to why they would want to stop them since it won't go on indefinitely. Profitable signature campaigns doesn't automatically imply that these art contests will continue running without any issues.
They switched from 'Number prediction contests' to 'Art contests' and they could switch again to some other kind of contests later on.
I think we all miss their contests here like « guess the multiplier » or « guess the slot » but with these art contests they also get something in return. They are, for the moment, the only casino doing this (already since quite a while) so they must see benefit in it.