In these days Microsoft is moving from wave 14 to wave 15 for Office 365 cloud installations. This means a service transition from Exchange 2010 Server backend to Exchange 2013 Server backend, Lync 2010 to Lync 2013 and other cool updates.
However, if you have travelled a long way to get a smooth migration setup (with all the back and forth of finding the right strategy and technical conditions) Microsoft can make you a big surprise by changing your Exchange target infrastructure. You started your migration project with Exchange 2010 in the cloud as target system and you end up with Exchange 2013.
This is “by design” when moving services to the cloud – as MVP Sean McNeill stated in his post [http://office365evangelist.com/?p=938]:
“This is an important questions because with a move to the cloud, the company give up some control on when, and even if, you will go through an upgrade of the service. The company now relies on the Service Provider, Microsoft in this case, to handle the upgrade and the cadence of the upgrades. This needs to be fully understood and accepted by a company moving to the Cloud.”
To mitigate the risk of forcing the customers to update in times where it is just neither “comfortable” nor “amusable” – as it might be in the middle of an Exchange migration project – Microsoft offers to postpone the update one time. The Office 365 admins receive a notification e-mail which announces the update schedule. From that information the customer has 3 weeks to decide that he better postpone or let Microsoft execute. When he decides to postpone, Microsoft will not start the update for the next 2 months. The timespan to complete the wave 15 upgrade is end of 2013 latest, which means your upgrade cannot be later than this deadline.
http://community.office365.com/en-us/wikis/upgrade/what-to-expect-during-the-service-upgrade.aspx
For more information check the Office 365 Upgrade Center: http://community.office365.com/en-us/wikis/upgrade/office-365-service-upgrade-center-for-enterprise.aspx
Dell/Quest Software seems to recognize first problems in running migration projects and recommends to postpone the Office 365 tenant upgrade by contacting Microsoft.
https://support.quest.com/SolutionDetail.aspx?id=SOL105116&pr=Notes+Migrator+for+Exchange
