If they included an adapter, then I would be less upset, but I doubt the Lightning port is as sturdy as the 3.5 mm audio jack, and that's what I'd miss. It ain't broke, so unless they use that additional space to make the battery larger, I'd pass.
And if they're doing it to make the phone even thinner, while keeping the battery the same, then f- them. Phones are so thin nowadays that I feel a phone case is a necessity now, not a option.