Long term? Minimal. All the niches it fills, have alternatives that would just grow to fill them in.

Short term? Catastrophic. Losing GMail and “login with Google” would leave a lot of people with no email, no way to login to other services, and no way to recover their passwords (through email). The loss of Photo backups would also upset many, Drive and Docs would leave a lot of people and businesses without their daily tools. Search would likely be the less affected, with plenty of alternatives already to pick from.