I think the larger point of the post above is that building an app for an in-vogue platform should be seen as a business opportunity. It is important to know it won't last forever, but that doesn't mean you shouldn't build apps for one of the most lucrative marketplaces of the moment.

You do need to realize that this can change fairly quickly, so you should either use this as a springboard to something else, or just accept that it's a temporary business and not something that will stick around.

The concept still applies even if the problem isn't about being kicked out (which a contract could maybe solve), but simply about the market fading for one reason or another. One common thing that can happen is that the platform provider may decide to compete with you, which is often very hard to come back from - they usually have access to the platform in ways you can't replicate.