This was posted on Sprint's website today:
Epic 4G users: We want to assure you that Froyo for the Epic 4G is still in the works. Sprint works very closely with our manufacturing partners to ensure that we deliver the best possible customer experience on our wireless devices. We approve the release of software updates when a new software version provided by the manufacturer can bring a better overall customer experience on the device. It is our intention to bring these updates to our customers as quickly as possible but only after they meet our rigorous testing criteria.
We can't provide any guidance on an exact or estimated release date at this time, but please know we are working to get Froyo out for the Epic as quickly as possible.
Source: Announcements: Statement about Android 2.2 (Froyo) Update for Samsung Epic 4G