Why? Those who ordered by 12/31 got exactly what they ordered. Tesla extending the deadline only gave more people an opportunity to buy cars with FUSC. The people who ordered later don't get anything more than the people who ordered earlier, and the people who ordered earlier aren't hurt by the people who ordered later. How is that unfair to people who ordered earlier?
If I had ordered on 1/15, my 7-day cancellation period would have extended to 1/22. 100D was announced on 1/20, I believe. I would have been able to cancel the order without cost or at least with the $500 change fee.