This entry by Gareth-Michael Skarka puts some concrete numbers from Comics & Games Retailer to the rather rickety state of the RPG industry. The numbers look, in a word, horrible. Clearly, the growth of MMORPGs and other factors are taking a big chunk out of the gaming world.
A lot of people seem to blame Wizards of the Coast and the d20 system for killing off a lot of companies in the RPG market... Wizards certainly has the strongest visibility in the RPG market, and enjoys penetration into the main-stream retail space that other publishers just can't match right now. I think as a result, Wizards has picked up more and more of the 'new gamer' market over the past several years, which has probably put the hurt on some other companies.
On the other hand, you could make the argument that really, Wizards is responsible for making the market as a whole larger than it previously was. TSR long had an edge in the 'new gamer' market that gave it a competitive advantage over the other systems. Dungeons & Dragons remains the single most recognizable name in gaming, and will remain so for the foreseeable future. Meanwhile, the d20 system and the OGL did a lot to lower the barrier to entry in the market for new publishers and new games. Potential writers no longer had to either convince an existing publisher to take a chance on them, or overcome consumers reluctance to learn a new, untried rules system. d20 meant that you could write your modules- whether it was a new setting, an expansion, an adventure, etc.- without worrying too much about the nuts and bolts of the rules. If your product made it to market, there was a large body of players and DMs that already knew and played by the same ruleset, and had a big hand up on learning or using your game. Even if your product couldn't stand on its own two feet, there was a good chance that if there was something worthwhile in it, people would be willing to buy it since it was so easy to incorporate things into other d20 games.
What I suspect happened is that this spawned a whole generation of hobbyists who thought they were going to be the next Gary Gygax, and tried to enter the traditional publishing market. The traditional publishing market, if you haven't heard, is hurting all over. Production costs are remaining high, demand and retail outlets have declined, and challenges from other media are threatening their consumer base and their bottom line. Add to that the fact that entering the publishing business involves managing issues of inventory and production that are capable of destroying even veteran players (TSR anyone?), and you have a recipe for disaster. Hundreds of new companies offering products in 1,000 different d20 lines simultaneously waded into the publishing business, unaware of what they were really getting into. It's little wonder that five years later, most of them are belly up in the tank.
The retail space has its own problems. Note that the figures that Skarka was quoting are primarily gathered by game retailers. RPGs are a perfect example of the sort of niche product that translates very well to Internet delivery- hence the 'long tail' discussion. The inevitable result is that as the number of gaming shops declines, more and more companies will go to direct sales and PDF distribution. And as more publishers make an end-run around retail distributors, more and more retailers are going to exit the business, either by going under or by deciding that it is no longer worth their time and money to be in the business of selling RPG products.
I try to support my local gaming stores on principle, but I can see a coming time when they just won't have a place in the market due to a combination of economics and redundancy. I've recently been thinking about buying the new Knights of the Grail supplement for WFRP. Now, do I buy that from Amazon for less than $20, or from a local retailer for $30+? What, really, other than instant gratification, am I getting from my local hobby shops? What are they getting from me? I do sometimes browse games in shops, and see things that I otherwise might not (though one place I shop occasionally shrink wraps all their games; very irritating), but is that really worth paying a premium for my games?
I think that gaming can survive losing the brick-and-mortar retail channel. I'm sure that retail could survive losing gaming (though it would be a hardship for some of the most dedicated retailers, which is a shame). Unless someone can come up with a more fruitful relationship for the two, they're going to have to.