I think you'll see RIM and Nokia slip even more because of Android. Don't expect an appreciable effect on Apple any time soon. Apple has locked in hundreds of thousands of developers, many of whom will also offer Android versions, but are unlikely to leave iOS.
Apple had the major share of the business market with their hardware
Apple never had the major share of the business market. Apple didn't even have the major share of the pre-PC general market, and then the PC beat the Apple II within a couple years of introduction in the early 80s. Macs never had close to the marketshare of the PCs.
The hardware manufacturer is irrelevant so long as devices are “cool” or “unique”.
That seems to be everybody's problem. Apple hardware is usually deemed to be cool by the buying public. Other manufacturers try to create cool, but the public rarely accepts it. Just look at the latest crop of smartphones. They all pretty much look the same except for the iPhone. With Apple's recent exclusive licensing of LiquidMetal's moldable alloys, I expect the trend to continue.
Remember the first ever spreadsheet Visicalc? Until Lotus 1-2-3 was released in 1983 it was the platform of choice for business and on the Apple II. In the late 70s and early 80s, the business choice was the Apple II.