I don’t understand how they are supposed to “sell your data” if you just never use a Mozilla account and uncheck all the telemetry. Its not like they can secretly steal your data, since its Open Source.
It seems to me like just more FUD that Google is spreading to undermine our trust in free software.
This has happened before in the software world, and its usually not a huge deal after a little bit of rockiness.
OpenOffice->LibreOffice. ddwrt->openwrt->tomato etc.
Development will continue, but maybe in a less resourced fashion.