It's up in the air at the moment, there has certainly been some discussion about Delve and possible retirement, it does somewhat feel increasing out of place these days and underdeveloped. Possible in the upcoming SharePoint event this month we could learn more or it might just slowly be deprecated, eventually. We don't know really, so this is just conjecture.
Much of Delve is now increasingly integrated into Office 365 and Windows 10 even with features like Sets, having a separate destination is less relevant. As to whether to promote it, that really depends on whether it's adding any value for your users and if it's complementing their Office 365 experience or if it's more a hindrance, as well other factors you mentioned.
