Here in Australia Telstra is offering existing BPOS customers the ability to upgrade to Office 365 early. Most BPOs customers should have already received an email inviting them to do just that. The first step in the process is to complete the early consent form here:
Telstra early migration consent form - www.telstra.com/business/office365consentform
There is also information at:
However, two worthwhile documents that provide checklists on the migration process are:
Early Transition Guide - http://g.microsoftonline.com/0rmcm00en-us/5040
Administrator checklist - http://g.microsoftonline.com/0rmcm00en-us/5003
Importantly, remember that Exchange Online in Office 365 doesn’t support Outlook 2003. That means that anyone using BPOS with Outlook 2003 will need to migrate before hand. That’s why those checklists are good as they give you things you need to be aware of prior to any migration.