No one means 'dead' like RIM, they mean 'dead' like IBM. IBM is doing great - they're making lots of money in the service industry, they have a good research division, etc. They also haven't made an impact in the consumer space for years, and they probably never will again. They're just a different animal now.
When PG wrote this, that's what Microsoft was. They were irrelevant in all the areas where interesting things were happening. Are they more relevant now? They seem like they might be, but it's hard to say. The essay is not about profit, it's about mindshare.
The fact that a large number of comments here are clarifying what he means by 'dead' is indicative of this baity nature of it. He specifically chose to say "Microsoft is dead" not "Microsoft has lost mindshare", and now its conveniently providing him protection by interpretation.
When PG wrote this, that's what Microsoft was. They were irrelevant in all the areas where interesting things were happening. Are they more relevant now? They seem like they might be, but it's hard to say. The essay is not about profit, it's about mindshare.