When you use a blackberry is it because:
1) Your company gave it to you.
2) You bought it knowing what you bought.
3) You bought it and have no clue.
If you're of the 1st type, you do not care, you may like it or not, your company bought it so you get the corporate email, updates to the OS and what can you run on the phone depends on two factors, how old the blackberry is, and how good the IT dep is. Corporates may find easier to keep buying new blackberries just because it is easier to do so, rather than jump the boat. So they're moderately loyal, and change blackberries every two or three years.
If you belong to the second type, you absolutely love your blackberry, you run the latest OS, and even knowing that an Iphone-like is better for the silly stuff, your blackberry is very convenient and they will take it away from your dead cold hands. You know its pros and cons. You're very loyal and will buy another blackberry, although you won't buy it tomorrow, you will buy it in the next two to three years, and maybe like me, you'll buy it once the old one breaks. But when you buy a new one, it will be probably high end model.
If you belong to the third type, no matter what, you'll think that the iphone-like or (whatever new market fashion) is great, you'll regret buying the blackberry, and more likely you won't buy another blackberry unlike it is even more flashy that the one being shown on tv.
So whatever happens, anyone having to spend more than £200 on a BBRY smart phone, won't be buying them in quantities, nor they will do it often. So I do not know how RIM or anyone else for that matter could expect to have a big market increase overnight.