The documentation with each release is not explicit about retiring pulses, while it has been made clear pulses will be replaced "in a future release" (link). This has us anxiously checking the docs for any mention on the subject before we upgrade.
There's currently no explicit date/version for complete deprecation. Currently the Dashboard Subscription functionality is being expanded even further, which is what Pulses are being deprecated in favor of.
I think we would develop a tool to convert the Pulses to Dashboard Subscriptions before removing Pulses completely.