This never made sense to me. These rumors claim that a Verizon iPhone will be released in early 2011. However, the iPhone's release cycle indicates that the next hardware update's due in June.
New hardware would be necessary for a Verizon iPhone (so it could work with CDMA), but if they were releasing new hardware, they'd likely have to fix the antenna issues.
If they did that, they'd then have two different hardware models on release cycles phase shifted by a few months from each other, and would have different hardware for different carriers--a sort of fragmentation that would massively complicate purchase of iPhones from Apple Stores. I just can't see Apple releasing a Verizon iPhone before June, or even releasing two separate pieces of hardware. It seems far more likely to me that they'd integrate CDMA and GSM into one phone, to avoid fragmentation and complication of the user experience.