With WhatsApp, Aren't BlackBerry Messenger And Apple's iMessage Redundant?

Thankfully with the advent of apps like WhatsApp, there is not much incentive left for newcomers to adopt a particular ecosystem, or for old-timers to jump to a new system- for messaging services alone. Of course, a ton of factors are at play like personal preference, quality and quantity in app store, budget etc.

Then, each ecosystem has its forte:
  • For Nokia, it's the maps and navigation in my opinion.
  • For iOS, the app store and the quality and delight in using the devices, plus being a status symbol.
  • For Blackberry, I guess the business tools.
Personally, I have used Nokia from young age, and now so much data (detailed contacts, calendar entries etc) is in it that I'm finding difficult to move to Android, or iPhone for lack of apps in Nokia Store.

Regarding Blackberry I'm confused- I mean is paying a fixed sum per month worth it, that's what I need to research more.