I kind of think my current configuration works well - I have a BB Bold 9900 and an iPad (both the BB and iPad connect into corporate email, calendaring, contacts). The BB is very good for regular email, phone, calendar, contacts, texting, viewing twitter feeds, and Weather app.
The iPad is great if you want to browse the net, read email attachments, books or other docs. I don't think an iPhone+iPad would work as well in this area although the iPhone and iPad do integrate together much better. But with RIM OS 7.1 I can use my BB as a 3G (actually HSPA+ whatever G that is - 3.5?) Wifi hotspot which means I likely don't need 3G/LTE on the iPad as much.
So IMHO RIM may have a future if it concentrates on what it does well.