Well, looks like I found my answer, http://community.office365.com/en-us/forums/154/p/43236/154656.aspxOpens a new window. It appears that the 5k limit is a firm limit. Looks like I'm going to have to control the view.
So we are using some calendars for a few different groups. It hasn't taken them long to top the 5k max item limit. I've been digging for awhile, and I can't find any way to alter this without CA (which SharePoint Online lacks). Any insight?