It seems to me like people who would (and can) otherwise buy internet will continue to buy internet, but people who couldn't afford it or didn't want to afford it might jump on cheaper packages. This is especially illustrated in e.g. third-world countries where we have majorities still not connected to the internet (where a super-cheap Google/Facebook/whatever package would go far), but there are still many, many people in poverty here in America that don't have access to basic things online. Offering them a cheaper plan to access just the parts of the internet they want to use seems like a win-win here.
As long as it doesn't go the other way.