It is a bit scaremongery because if you're using it for backup you can just switch to another service if they announce its pending retirement. It's an inconvenience for sure, but not truly a significant reason to not go with Google.

Besides, who knows where Dropbox or anyone else will be in 5 years. In 5 years they'll need to be turning a profit which could have a major impact on product and pricing, especially for the "backup" use case.

Incidentally if backup is what you want, check out an optimized service like Backblaze.. $5/month unlimited storage.