That's true! When that happened to me while I was overseas a few years ago. I flew to Vancouver and took Amtrak back to LA. My passport card was still valid for another few years at that time and it worked perfectly for re-entering the US by train.

Earlier this week, I accompanied my grandmother-in-law to the local US Passport Agency because she needed a new passport at last minute. We showed up as soon as they opened. The security guys didn't care that she was almost 3 hours earlier than her scheduled appointment time.(nice to play the "young man, I'm old and I don't have a lot of time waiting around" card) The clerk processed her renewal and we came back at 2pm to pick up her new passport. Still the current design, obviously.

However, I did chat with the passport clerk about the "new" passport. She said "early 2018 at the earliest" was what they were told recently.