Mailbox quotas for E3 and E5 accounts is increasing to 100 GB, with all other Office 365 Exchange mailboxes remaining at 50 GB, including Business, E1, shared, resource, group and public folder mailboxes. Administrators don't need to do anything to increase the size of existing mailboxes, as the change rolls out, mailbox sizes will be increased automatically.
A list of all mailbox quota sizes is at Exchange Online Limits - Mailbox storage limits. Additionally, this page lists the limits for other Office 365 features.