Apparently, the BBM app for Android and iOS has been received pretty well, perhaps in small (or large) part to some shady marketing tactics, too. Either way, it seems 10 million people have already downloaded the app within the first 24h, which isn't too bad for a chat app/SMS alternative from a company that's in talks to be acquired or sold for parts. Now, the question is what does this mean for Blackberry, the company, and can an app alone save them?
I think it can not, because it's just one free app, and even if it would be downloaded 100 million times, I don't see how it could make Blackberry enough money to keep them in business. Maybe if they did this a couple of years ago, when they were still very reluctant to release BBM on other platforms, because they thought that through BBM lock-in they'd keep users on BBM, they would've had a chance with it.
One of Blackberry's fatal mistakes was that it believed things such as their physical keyboards or BBM would keep users away from beautiful and much more powerful touchscreen smartphones from competitors, that were based on platforms with many times more apps, and better apps, too. It seems Blackberry overestimated how much people love Blackberry keyboards and the BBM service, and underestimated the competition's app advantage.
I don't think Blackberry is even seriously considering keeping the company for themselves, and see how far they can go with BBM. It's too late for that. But a successful launch of BBM, would perhaps convince the buyers to pay a little more for the company, since companies with a large user base, tend to be valued very highly, even if they aren't making any money (see Instagram, and other web services).
Google is considering buying parts of Blackberry, too, and while it's probably most interested in buying some patents from them, they could be interested in getting their BBM userbase, too, and transition them to Hangouts later. Whoever is buying BBM will either have to keep it and expand it, or transition it into a larger chat service, because otherwise its users will probably be pretty angry if they just shut it down.