To me it's still not too late for RIM. All they need to do is sell a phone that has a slide out keyboard but the rest of it is touch screen (with an option to use a touch screen keyboard as well), and drop their own OS and use Android.When the iPhone was first released, 3.5" was the perfect size for a phone. However after mobile gaming and browsing really took off, there was definitely a need for a larger screen to appreciate and utilise more content.
Regrettably Apple's defiance and insistence that the one-handed use of a phone is imperative will give the haters quite a lot of ammunition once Apple do release a larger screen with their next phone. Nonetheless they are making the right move and although it's potentially a couple of years too late, they're not yet in a position where it's too little, too late -- as arguably it is with RIM.
If they did this I think they could make a comeback. It was only a year or two ago that it was between the iPhone and the Samsung Galaxy phones in the smart phone market that no one could break. Now we have valid competition from both HTC, and Sony, both of which I would say offer better phones than the latest Galaxy is.