Regardless of wishful thinking, at the very least it removes any finality from the anime's conclusion
This weekend, the Re:Zero anime ended. (Have you watched the finale yet?) Volume 9 of Tappei Nagatsuki's light novel series (released in North America by Yen Press), with material from that last episode, and the continuing story, is out September 25th. So, it's time for fans' attention to turn from the animated version of the story to the prose. An Akihabara billboard has helped them along the way.
Still, Japanese fans are reading, or at least hoping, that there's some implicit suggestion of a second anime production being developed. At the very least it removes any finality from the anime's conclusion.
"Even if the animated story is over, the original story doesn't end. The ongoing story can't end here!"
Also, Yūsuke Kobayashi (Natsuki Subaru) and Rie Takahashi (Emilia) saying thank-you and goodbye on the series' web radio program...