Yes, I saw many reports early on of how iOS 11 tanked battery life on the SE. All of the SE's in our household are remaining on 10.3.3 until they are replaced. (or some critical app requires an update to 11+) Battery life is still great on them.I have a few different SE’s. I consistently get 2 days of usage in the 10.3.3 devices. On iOS 11, I just a normal day of use and it’s almost at zero. The difference is crazy noticeable...night and day.
I think that the analyst estimates are way overblown. As as been previously stated, not everyone affected will hear about the battery replacement program. Of those that do, a fraction of them will take the time to get it done (if they live within a reasonable distance of an Apple store), and still others are on some kind of regular replacement schedule that they're paying for so they'll simply "upgrade" to the next phone.
If there is any financial impact to Apple as a result of this battery issue, it will be negligible... if the comments on this forum are any indication. Nearly all of those who are upset about this issue are still planning to continue buying iPhones.