You don't have to sponsor anything. We'll continue to add features based on demand, and when this rises in priority over other heavily requested items we'll consider adding it. Sponsored development lets you put your money where your mouth is. We find that people will up vote all kinds of features, but when they are willing to actually pay for them they show that they really need it. If you're not willing to pay for it, then it's probably not much of a requirement for you. Every feature we add has an internal cost to us, often significantly so, so we have to prioritize based on demand.
Regarding paid modules, that is an option, but a module that only 3 or 4 people would use would be priced considerably higher than a module 3 or 4 hundred people would use. Modules that drive demand are already being created by 3rd party developers, quite a few of them, actually. But an authentication scheme is neither a module or a plugin, but a core feature, one we would not be able to charge extra for.