“Inbox is an email company. Google is an advertising company. This product is our focus, and will not be ‘discontinued’ unexpectedly.” Burn! Very amusing. But for all we know they will be acqui-hired, maybe even by Google, and then shifted to a different project.
Yuuuuuup.
If you're a company that wants to prove that you actually care about providing services that customers can rely on then you need to make a financial and legal commitment to that statement. Create a legal entity tasked with carrying out continuing operations in the event that the company shuts down, set up a bond or other funding source set aside which will provide enough operating budget for operations at some level to be continued for a year or several years.