Pearl series I believe have from the start been some kind of experiment rather than serious devices from RIM. They wanted to capture a portion of the consumer market and have more users get interest in BlackBerrys. Original Pearl (8100 and later 8110/8120) design is in my opinion a great one, but SureType is not for everyone (read: good for English, but no other language, which is why the Pearl isn't so succesful). Pearl Flip improves the design (keyboard to be specific) much, but at the cost of going "flip". I know that most consumers right now aren't after flip phones, rather touch screen devices (for which Storm2 should be just fine).
Maybe never? I foresee a death to the Pearl series.
I unfortunately agree with shinkodachi -- there is no technical reason why they cannot, but it's a marketing and business reason. If they start to see sales of their high-end slipping to the iPhone, then they might have to get creative with the Pearl.
The perspective of SureType is interesting, and I never thought about that. Nevertheless, SureType could still address at least 1/4 of the world's population that can read/write, for English, but also a lot of European languages.