Shadowhunters Ending with 3B in Spring ’19

Freeform made the SHOCKING announcement today that they are ending their fan-favorite series, Shadowhunters. I, for one, did not see that coming! Here’s the official word:
“We are very proud of Shadowhunters, a series that broke new ground in the genre world and became a fan favorite. However, along with our partners at Constantin, we reached the very difficult decision not to renew the show for a fourth season.”
The final 12 episodes will air in the spring of 2019, with a special 2-part finale meant to give “devoted fans a proper ending.”
Are you as upset as I am? I’m guessing it’s because of declining ratings (check out the S3 numbers on TV Series Finale). Fans, where’d you go?
Now I worry they’ll make a messy rush to tie things up in a pretty bow. And what parts of the book series will we never see? Will the extra 2 hours be one big epilogue?
I guess, really, there’s only one thing left to say: Veni. Vidi. Amavi.