rrkpl, at least in the short term*, the iCloud switch shouldn't affect the ability to export information to iCal at all, which is what it sounds like you're using. That feature is an export though, rather than sync. (iCal *sync* is a different feature that doesn't include deadline reminders.)
To export deadline reminders to iCal, just open OmniFocus' Sync preferences and ensure that the "publish due reminders as a calendar" box is checked. You can then use the "Subscribe in iCal" button to make sure your copy of iCal on that Mac is getting the information. There's a similar process on your mobile devices.
*If you're currently syncing via an iDisk, Apple's removing that option in June of next year, but you can switch to the
Omni Sync Server anytime between now and then - we're not going to charge for sync access.