There are stability considerations too. They don't want the Bluetooth Berries to be like a bloated 7750. I'm sure that waiting till 4.1 is probably a prudent move to shake out 4.0 first in the market. I'm making sure they didn't forget about the possibility of keyboards!
Right tool for the moment -- I'll expand on that. It also relates personally, since I am deaf, and keyboards are the main method of communication. I still often carry around my iPaq sometimes only just because of compatibility of full size keyboard. If I carry around the laptop, I don't need the folding keyboard, but when I go to restaurants and such, and talk to my significant other, or something, I find communication to be faster on a full size keyboard than spoken speech which must be worded carefully and spoken slowly. And it's hard for me to lipread others. (I type faster than I can speak clearly -- 132 WPM with 97% accuracy in a recent test at http://www.typingtest.com
Huckleberry Finn 1-minute test paragraph). So if I am doing business travel or travelling on the train between cities, I will bring the laptop. (And that is where BlackberryModem comes in). But if I am socializing with friends or significant other, then I use my iPaq with the folding keyboard to type back and fourth. I can put iPaq in left pocket and keyboard in right pocket. Complete discreet concealment cannot be done with a laptop. More information on my hearing impairment at the marky.com site. Anyway, now you know what I mean about the right tool for the right moment. Most will just stick to one (ie laptop) and desire BlackBerryModem, while others prefer leaving laptop behind and just bringing a PDA and keyboard (ie ThinkOutside folding keyboard). A select few would use both for the right tool at the right moment (like me).