While I wish to be as positive as you are about the future there still few points I feel important to make.
* First of all I don't think that important projects started by single developer is right example for benefit that BI could bring because they managed without basic income in past and they don't need it today.
If project don't get enough traction during period when project originator actively work on it that's usually mean that will never happen. But if original developer leave there still chance for someone else who believe in idea to take control or just fork it and continue. Also this rotation seems like one of crucial parts that make open source successful.
So while BI would let someone to work on the same code indefinitely or at least much longer than now I don't think that will greatly increase number of popular and widely used open source projects. And who knows might be it's will even decrease that number.
* Another note about voluntarism. It's great that in developed countries there is endless number of ways for society to participate in all kind of useful activities and I wish it's was even remotely close in country of my origin. Though for the reasons stated before I simply don't believe that crowd-sourcing can be applied to build successful software projects. You might say that community can go promote software instead of helping with development, but today you can't even promote project efficiently using centralized tools we have simply because companies companies like Facebook and others want you to pay for that. Number of communities outside of centralized social networks is dwindle over last 10 years.
So I wish to think positively, but so far all I see is that distributed FOSS projects cannot successfully compete with corporate or VC funded products. With direction where Internet, hardware trends, Internet and society itself going I don't see how we going to get more people involved in open source and not less.
But hopefully someone will come up with idea how to fund truly distributed open source teams so they can at least somewhat compete with VC money burning centralized proprietary alternatives. Without that best we can hope for is that open source will keep positions it's have today.