It is very likely the government can remove the flash memory chip in the phone and save the contents. After doing so they can wipe them out over and over again trying to break the code without the risk of losing the original encrypted data.
The risk isn't losing the encrypted data - it is the risk of losing the encryption KEY. That key is a taken from a combination of the pin/passcode (which can either be numeric or alphanumeric in iOS 9), a 128-character identifier unique to the specific phone, and a random number known as a "salt". This combination of characters is then run through an algorithm to devise the actual encryption key. If the key is erased from the phone, it is virtually impossible to recreate the same key. Even if you knew the identifier and the pin and tried to recreate the key, you wouldn't get the same one because the "salt" would be different.