How to put a token in field Simplenews -> Subscribtion block -> block message
It's likely there's no off-the-shelf solution here. The block message field is a variable in the Simplenews module. It's not possible to make variables dynamic; there's no hook to override variable values.

In order to make something like this happen, you'd have to use a combination hook_form_alter() to change the block setting form &amp; hook_block_view_alter() to alter the output of the Simplenews block.