I think you are free to put your "will" everywhere you like and think it'll be found.

IMHO from a general legal and organizational point of view, it should be somehow like and near the licence information in your module.

Different people will want to handle it differently on a module's basis (competence varies, a DBI expert might not be the best to handle a Tk module) and general schemes would be nice (like hypothetical "in case of longer absence the Saints of PerlMonk should poll" or "the most depending CPAN authors should decide").

BUT from a practical view people are reluctant to talk about their own death, so hiding it in Makefile or Meta sounds more feasible.

In the end it should be somewhere where the CPAN admins can easily retrieve and handle it.

edit

And "absence" should be defined, being 10 years coma or going missing in an Asian land war (freely citing Brian d Foy) are not much better.

Probably all of this is better handled by an institutionalized fork and branch technique... ?

PS: In case of my own death, I want all my PM posts to be edited and translated to Japanese Haikus. ;-)