Unless they radically changed things for 4th Edition, that's not what happened.
The concept (with Shadowrun and Earthdawn) is that the Earth's "manasphere" undergoes fluctuations over millenia, thus the strength of "magic" goes through cyclical changes. The Shadowrun setting is during an upswing of the mana cycle, thus magic is on the rise. As well as spellcasting, various genotypes and diseases are surpressed in a low mana era, hence the sudden appearance of fantasy races and monsters as the mana levels become high enough for them to be expressed again.
Perhaps you're getting confused with the Halley's Comet arc, which was basically an excuse to introduce *even more* magical things into the setting when Halley's Comet passes by.
Good comic, BTW :)