if the MarkIII was released without major issues it wouldn't be time to replace it...its time...
Canon is clearly sweeping the 1D line under the carpet. That is why they released the 5DmkII. To sweep the 1Ds under the carpet.
If Canon released a MarkIIIn or gave a "rebate" to MarkIII owners, it would be admitting there was a problem. Having already released a MarkIIn, having another "n" would be super bad for Canon PR. That would be two consecutive cameras that need "fixing"
Rather than "fixing" those cameras, they simply want people to forget about them, by releasing cheaper cameras with similar / better capabilities.
I assume the 1D MarkIII will be forgotten soon as well.
--
-shawn