It seems a fairly safe bet that the near future will include an increasing emphasis on micro-transactions in subscription MMOGs. Indeed, I'd have to say a much better question than if it will happen is how quickly. With this as a starting point, I recently found myself wondering what other changes we might see before long in terms of how titles are monetized. Then and since, a number of interesting possibilities came to mind.
Premium Service Tiers
What I'm thinking of here is subscription or membership levels that cost more than the standard monthly fees and provide additional benefits. SOE tried a version of this a few years ago, and it didn't do well. This doesn't mean the concept isn't viable, just that the implementation in question did not succeed. I suspect multiple factors contributed to this outcome, a key one being that the market simply wasn't ready.
Is it now? I think it's at a stage now where a well thought-out package could work. Note that I'm not saying what was tried before will fly now. There's no shortage of other possibilities, and they don't all include the element that may have been the most contentious: segregated servers. At this time, I'm not prepared to speculate as to what I consider likely to succeed - at least not for public consumption. However, I believe various publishers are trying to figure out exactly what they can do, and also that some will try something.
Limited Service Tiers
If a company regards the idea of paying the full monthly fee as a barrier to entry, the binary thinking approach of lowering it to nothing isn't the only option. There are other possible amounts in between. For instance, let's say I'm interested in trying out a particular game, but not eager to sign up for $15 a month. If there's a free trial that lets me experience enough to decide, fine. But what if I think it's too restricted? To use a concrete example, what if I blow through the WoW starter edition in a few hours and still want a better sense of the entire game than what I've gotten while reaching level 10?
Perhaps I'd appreciate the option to pay something less than the full $15 for a limited time with most of the free trial's restrictions removed, maybe something like $5 for 20 more hours of playing time. I get the chance to make a better-informed decision about subscribing, while Blizzard gets longer to snare me plus a roughly prorated full fee.
Another possible alternative, one that isn't mutually exclusive, is a lower-cost time limited tier. This would suit players who know they will only put in fewer hours than most. As it stands, they have to choose between shelling out the full fee and leaving the game. But what if they could pay say half-price by accepting a cap of 15 hours? While it's a virtual certainty that such an approach won't sit well in some quarters, it seems likely to help attract and retain certain types of players. Of course, some people paying $15 would opt for it, so some revenue would be lost; the key question is whether there would be a net gain.
More Exclusive Items for Subscribers and Members
We've already seen how popular micro-transaction items can be in WoW, which means they can generate large amounts of money. Sure, no other game has a user base of a similar magnitude, so the absolute number of dollars would be difficult if not impossible to match, but selling enough to be meaningful on a title's own financial scale is what truly matters more.
I'm not expecting companies to jump in the proverbial deep end by going from offering no exclusive items to a huge range. What's more likely is that we'll see them creep in. If and when a sufficient degree of negative reaction builds up, it's always possible to scale back or stop. Until then, why not give players more ways to spend their money?
Higher Cost Items
This is obviously contentious. However, the fact of the matter is that there are some people out there who are willing to spend sums that most would never even consider - if they're given the opportunity. In this regard, the example that springs to mind is a Chinese "whale" (a term some other industries use for big spenders) who reportedly paid the equivalent of $20,000 for a unique weapon. What's more, I'd hazard a guess that this was completely additional revenue since it's hard to envision such an individual reducing his or her normal buying pattern for potions, vanity gear, etc.
While there aren't many players with that kind of money to spend, there's also a very wide and basically unfilled gap between what is presently the high price range and $20,000. I doubt we'll see many offerings if any up where the air is that thin, but it seems inevitable that publishers will stretch the current upper limit. Yes, I'm aware EVE's recent attempt didn't go well. But that title's community is relatively atypical. And as above, this doesn't prove the general concept won't work.
More Non-Vanity Items
This kind of goes hand in hand with the previous one in that it takes more perceived benefit to encourage someone to spend a larger sum of money. So, to make higher-priced items attractive enough to buy, some of them will give their owners in-game advantages. The trick is to balance them so they're meaningful to the buyers, but not enough to seem overwhelming to the degree where significant numbers of players leave.
This isn't nearly a complete list of possibilities, so imagine what else might be coming...