Hi,
our current deprecation policy is not so well defined (see e.g. [0]), and it seems to me that it's something like:
 1) deprecate something and add a DeprecationWarning;
 2) forget about it after a while;
 3) wait a few versions until someone notices it;
 4) actually remove it;

I suggest to follow the following process:
 1) deprecate something and add a DeprecationWarning;
 2) decide how long the deprecation should last;
 3) use the deprecated-remove[1] directive to document it;
 4) add a test that fails after the update so that we remember to remove it[2];