Hi cdhcpa,
1. No. The SkyDrive and Office 365 are two separate services and they cannot "share"/"link" accounts.
2. Could you provide more detailed information about the question? SkyDrive Pro is a part of Office 365 Preview; you can sign in SkyDrive Pro with your Office 365 Preview account.
3. Currently, it is not available to migrate P1 pan to Office 365 Preview, please keep monitor Microsoft official website and this community to get latest information.
4. You can remove your custom domain from P1 plan and add this domain in your Office 365 Preview account. To protect email data, please use PST file:
http://help.outlook.com/en-us/140/dd401503(d=loband).aspx?sl=1
Note: all data in the Preview account will be deleted when the Preview ends, including email and calendar data.
Office 365 Preview FAQ: http://www.microsoft.com/office/preview/en/faq
5. Yes. Please monitor Microsoft website for the detailed timeline and information.
Office 365 Service Upgrade Center
E plan: http://community.office365.com/en-us/wikis/office_365_service_updates/office-365-service-upgrade-center-for-enterprise.aspx
P plan: http://community.office365.com/en-us/wikis/office_365_service_updates/office-365-service-upgrade-center-for-small-business.aspx
Thanks,
Bourne Zhang