I was (silently) proposing getting a corporate GS4 or iP5 and running the BBM app on it.
If you like their hardware, you must have something in mind. I think it's a dead-end choice, myself. They are shrinking and in "do whatever is necessary to save the ship"-mode (including talk of taking the company private). They won't be able to afford compelling new hardware for a while.
The Z10 seems to be their latest gadget on AT&T - http://www.att.com/s...s/blackberry.html - no keyboard. The Q10 has a keyboard.
It's probably not worth agonizing over given all the unknowns. Use whatever your colleagues/boss use or recommend and move on. You don't want to be in a situation where they send you something and your gadget doesn't work with it 100%, so waiting on a BBM app (unless it is immanent) is risky.
HTH a little.
Cheers,
Scott.