It has been reported that Robert ,a reader of MacRumors, has contacted Apple CEO Tim Cook via email regarding a query on how to merge more than one Apple IDs and in reply the reply on phone call Apple employee said,
while the company did not currently offer any way to merge different Apple IDs, it was working on a solution for the problem.
iCloud can be integrated once on the device and when completed you can not use another ID except waiting for 90 days period. iCloud also provided procedure to migrate Apple ID data into iCloud however its limited to one Apple ID so there should be a way to merge more than one Apple IDs before migration to iCloud.
We have recently covered iCloud in detail including iCloud Launch, iCloud TV, iCloud Web Access, iCloud integration and iCloud Find my Mac Service. Now Apple has allowed developers to migrate their MobileMe accounts to iCloud via new portal MobileMe Move.
In this process Apple will migrate your Mail, Contacts and Calender entries to iCloud whereas users can keep using iWeb, iDisk, and Photo Gallery till 30 June 2012. Moreover Dock item sync, keychains, dashboard widget sync, mail account rules, signatures, mail smart boxes, and mail preferences will not be available after the process. Therefore you can manually back them up and use in iCloud after migration.
Note: This procedure is only valid for Apple Developer Accounts Only.
You can have a sneak peak into iCloud by following procedure here.