Gamasutra has a feature called "Episodic Gaming in the Age of Digital Distribution": "At the heart of the debate about episodic gaming, we believe there is a push toward Gaming as a Service"
It raises several interesting points - including the distribution of games content, risk-reward and the aspect of lock-in.
Distribution - almost a "must have" to make episodes feasible, from the days of short films every weekend, via tv episodes to podcasts with a dedicated rss feed. The attention of the audience and the cost must match up, which is why X-box Live is so cheap for low level membership and why Steam needed something huge like Half Life 2 and Counter Strike Source to get off the ground.
Risk - it is easier to get a spin-off from something popular than to start a new franchise from scratch. If you have to both create the world, characters and story - as well as educate the masses, and develop the core system, the episode is no cheaper than the original. But if you already have the fan-base (ref Marvel comicbooks minority of total revenues) then the episode or sequel is that much easier to do.
This can already be seen by the "adver-games" [1, 2]- small flash games used as part of a major advertizing campaign, where the concept and story is already created (sometimes the game as well, it is just reskinned for the occasion) and put before the audience.
Lock-in - with more and more content available; books, movies, tv shows online or on dvd, multiple games systems, tens or hundreds of MMOs - there is a much stronger case for building up direct consumer relationsships for all parts of the valuechain (ip owner/creator - developer - publisher - distributor - retailer). It is in part why Nintendo is still going strong (financially if not in terms of absolute marketshare for consoles) - they own the Mario franchise, so they can control how it is used and by whom, making it easy to come to market with new spin-offs or sequels.
With the improved X-box Live Microsoft is giving the 360 a better chance of being the first stop for consumers - and the stats show that short casual games are a (excuse the pun) "Killer App". Why pay a lot to learn something new, when you can test something just as captivating for five or ten minutes? Sure the hard core will still want their Halo 15 and Doom 2073, but for mass-market a short, risk-free and compelling piece of entertainment is key. Be that a "15 minutes weekly in-between episodes game" for TV hits like Lost - or a discussion forum with other fans...
In other words: the future is still wide open, and the chance of there being "one right and final solution" is a big in episodic games as in business in general: slim to none, but good for a rant or book
