Doubt it, RIM already has their own operating system, although it may be that D is RIM.
They've got major catching up to do; internal development doesn't seem fast enough. We're nearly midway through 2010 and the closest to a decent browser that they've delivered is a few leaked images.
I will agree that their OS is lacking in many areas compared to many of the newcomers in this space, but that doesn't mean they run out and buy another failed phone OS for a whole lot of money in exchange a few features their rapidly growing team could implement or a smaller acquisition like their purchase of Torch Mobile could deliver. RIM's main focus is also more enterprise customers than consumer and the feature set demands of their customers are a little different.
From a historical perspective (not sure if it is currently true), Palm's customer base would have lined up well with RIM's, too.
Has webOS really failed?
This whole discussion is speculation... Once can objectively state that RIM is pretty far behind in delivering a modern mobile OS, even those targeting enterprise customers. I didn't even mention the fact that application development for the platform is somewhat of a nightmare, something that will be increasingly important to a CIO.
Regardless, arguably, the consumer market is in fact a lot more important to the company both today and going forward than you've made note of. Look at the company's marketing material: it is generally centered around media playback or BBM.
Buying Palm, porting BBM to WebOS, and slapping the Blackberry logo onto the Pre and Pixi would be a pretty easy way to improve their position in the consumer market.
The only reason they could buy RIM is if they wanted to do their own line of consumer phones, and from what we have seen, Palm has not really taken off yet. So it would be better for RIM to focus on improving their own OS, dumb it down a bit for new users.