It's late for BlackBerry releasing the iOS and Android versions of BBM. WhatsApp, Wechat and LINE are popular in the world. However, It's a piece of good news for Blackberry fans. I am not a real fan, but a semi-fan of blackberry, since I don't have any blackberry phones, however, I have installed a BBM on my phone. I tried the BBM. I think it's nothing better than WeChat, which is very popular in China. It's a little out of date.
BBM says: "BBM™ is the best way to connect and share instant messages, pictures and more for free, in real time. Download the app today." [1]
WeChat says: "Connect with friends across platforms" [2]
Line says: "Free Calls & Messages -- LINE, a communication app for free calls and messages" [3]
I have to acknowledge that BBs were good phones, even the best ones before Apple released iPhone. But the Z10 and Q10 have not make BlackBerry rebound from years' loss yet. Although BB performed well at the "911", Obama shew his BB in the 2008 president election of USA. But the BBs are phones for small slices of population.
I am negative that BBM would save BlackBerry at once. However, there's a chance. Make people stick to use it, make it better, make more apps related to BBM. I think BBM may provide email service for saving their chats if customers want.
BBM Video and Voice are not available to iOS and Android customers, yet. I think that's a good oppotunity for BBM. But instant video and voice are nothing new, and WeChat, LINE provide them.
References:
[1] http://us.blackberry.com/bbm.html
[2] http://wechat.com/en/
[3] http://line.naver.jp/en/