This may be a little OT, but I think this type of notification, along with Apple's announced plans to start culling old apps from the App store that don't meet minimum technical requirements, is of most concern to fringe or abandoned apps.
I do think that Indigo will have to embrace, at some point, switching their development methodology from the classic "Waterfall" approach of gigantic mega-releases once very five years (sorry, couldn't resist that!) to the currently widely adopted web services and mobile apps agile development paradigm of rapid incremental development and deployment.
Especially with the software industry moving to subscriptions and rewarding paying customers/subscribers with a constant stream of incremental updates, it will be harder for Indigo to adopt a subscription/maintenance fee pricing model if they only deliver changes once very xxx months or yyy years.
https://en.wikipedia.org/wiki/Waterfall_model