I'm not so sure (for reasonable values of "forever"). From what I see, once some software hits a critical mass, it's nearly inextricable.

Look at Microsoft. Before they became a major player, the dominant OS and computer system would seem to shift every couple of years; Amiga, Commodore, Apple, etc., but once Microsoft became a major player they never really lost their grip. They continue to maintain that grip simply because so many people were familiarized on their systems and so much software was written for those systems. Does anyone really believe that someone looks at OS X and Windows these days and decides that Windows is objectively superior? Most people, even technical people who hate Apple's MO, would admit that OS X is better on its merits alone.

The reason that MS has dominated and continues to dominate is because of the software available for the platform. It's all about lock-in. People don't use Windows because it has more compelling features than OS X, they use Windows because they want to play games, buy software off the shelf and know it will run without any problems, or run their company's internal software.

Let's take Facebook as another example. For years there was a pretty constant, roughly bi-annual shift in the most prominent "social networking" site; LiveJournal, Friendster, Xanga, etc., until Facebook. Around 2008 Facebook began eating MySpace's lunch and Facebook remains undisputed social networking champ today with no signs of slowage.

I'm concerned that Facebook is the new Microsoft -- it has become the de-facto standard, and despite any number of superior features that may be developed in other systems, it doesn't look like anyone is going to be able to challenge Facebook seriously. Some would say that Google was perhaps the most worthy challenger, but even they have failed to really make a dent despite the fact that most of the world visits their search and email services daily.

I'm not sure exactly where that critical mass gets hit but I think it's hard to reverse once it happens. Maybe it's something like, "Once your grandparents use a certain program because everyone else does, it's relatively safe to call it 'ingrained'." I know that my grandma had no compulsion to create a MySpace profile even though she constantly [attempts to] check[s] Facebook now, and I also know that it'd be extremely difficult to train her to use a non-Windows interface.