I have this strange feeling that we are only seeing the surface of what's about to happen at WotC... Please follow along and remember that this is PURE SPECULATION.
Prelude: About 3 years ago (or maybe more I can't remember) WotC took their flagship game M: tG and put it online in a digital format so that you could play around the world and open things up to those players in remote or isolated markets. (growing up in a town of 350 with no major access to 'big cities' I have to admit, it was a brilliant marketing move). It has been modestly successful and has had a steadily growing audience. Apparently to the point that with the exception of tournaments, the whole of the game has seen a slight decline in 'normal - real world' sales.
The intro: At GenCon this year, the Roleplaying public is treated to the surprise that D&D is getting a new edition, oh and BTW, there will be parallel digital material AND increased functionality that will be available online. Now with the digital tabletop you can play across the waves or in the next county without having to be face to face, while still being able to enjoy your normal table top experience.
The future and the hook: What I see is a great way for WotC to update their materials and snag a share of the smaller markets (which when added together makes a HUGE chunk of people), combine revenues , focus design and development WITHOUT having to reprint and waste money on manufacture, print and shipping costs to get to these otherwise lonely outposts of geekdom. In other words, increased sales and decreased overhead. I expect this Gleemax thing to be VERY rocky at first, but in the near future I would expect to see a mass migration of every WotC program and product that they can conceivably convert to an electronic format to the Gleemax model.
The DDI: essentially, DDI will be the Dungeons & Dragons component in the larger Gleemax schema. For example, What if in the 90s, Dragon, Dungeon, Scry, Shadis, and Electronic Gaming magazines had been combined into one publication with no loss of material and only a small price increase was tacked on? Would you have bought it to have all your geek related material in one handy package? But what if you didn't play electronic games or think CCG were cool?
This is what I believe WotC is doing with Gleemax, a super online digital magazine that will eventually cover all the bases with each section specifically expanded to meet the needs of that community. Eventually I would see the price being handled as a 'buffet' style menu of which sections (not which features in those sections) you would use. Access to the Forums, free, DDI a small monthly fee, DDI and online M:tG, a slightly larger, but discounted fee, etc.
Of course I have nothing to base this on except good business sense. And whether or not anyone wants to admit it, regardless of the quality of product and the respect of the gaming community, WotC has made a ton of really good business decisions