After a while, the skimage namespace will be nothing more than a shell. There will be no image processing code inside, only the porting instructions remain. So, carrying that around won’t be much of a maintenance burden—it’s essentially just documentation.
It is true, this may happen in some cases, in which case we will need to duplicate some code back into the old namespace. I hope that those cases are few, but there is no technical barrier to making this work.