To cancel a show with declinig ratings/viewers is a normal process, but with Warehouse 13 it should not go this way and not that fast.
Warehouse 13 has humor, style, good and likeable actors, interesting stories and locations, and is sometimes thrilling. There are good actors, nice scripts, fine guest stars, interesting and far-fetched stories and premises, mostly well, when not, from time to time, brilliantly executed.
Furthermore, it's potential is far not exhausted by now, one can imagine a lot of other locations, enemies, dangers, story arcs for at least two or three further seasons. Then I would say, lets's rest it in peace.
People of all ages do like W13 for one of the characteristics mentioned above.
And maybe some kids are motivated to find out the truth about historic events and persons occuring in the show, like the Count of Saint Germain (superbly depicted by James Marsters), or now Paracelsus, who was of course not a rude alchemist but an ambitious medical doctor (Agrippa von Nettesheim would have been better as he was more an experimenting alchemist than Paracelsus).
Why the ratings really declined has to be carefully analyzed and then there have to be taken the proper measures to correct, which I would locate in better storytelling/scriptwriting/evolving the charcters and so on. If the stories have become too routinely, there should be a bunch of good writers out there to help, I would recommend Steven Moffat from 'Dr. Who' ;-)
To throw away a gem is of no good for the thrower. And W13 is a rare gem of a show that is simply engoying most of its especially when it shines, which occurs not so seldom.
What I mainly hate about this decision is that there seems to be no way to continue the show on another channel. They cannot go for a Warehouse 13.1 or 14 (which should be then located in -- China ? sorry for the little joke) say, on NBC or Fox, if Syfy won't let them, and they won't for sure.
I think there should be a huge outburst of resistance against the cancellation of W13. Only this could make the Channel rethink and renew. Please, people, do something about !
(and please excuse my bad English)