"If mainstreaming happens, there is not going to be enough SP to service all people so the idea of earning for everyone is ridiculous"
Surely if mainstreaming happens, SP will be worth SO much more that it will take much less of it to service each person.
That said, people only have so much attention to go round. If I am following ten other people whose content I like, then person number eleven is going to suffer, because I simply don't have time in the day to read an eleventh article.
So, maybe even if there is enough SP to service everyone, on account of one SP being worth considerably more than it is now, the vast majority will have to settle for being audience members because the most talented, most considerate producers will command everyone's limited attention.