i really missed out on Pokemon events for the past few years and I am wondering when the next one is coming.
There doesn't seem to be any new Pokemon events coming for Pokemon Black/White since it's getting old. All the new Pokemon events will be for Pokemon X/Y. The current Pokemon event for X/Y is the Speed Boost Torchic with the Blazikenite.
Here is a link for all the Pokemon events for Black/White: http://www.serebii.net/blackwhite/wifievents.shtml
As you can see there hasn't been any new events since the Darkrai WiFi event.
The next event to come is the Celebi event in X and Y.If you get access to Pokemon Bank until 30th of September 2014 you will receive this Celebi.
Click to the link and scroll down unlti you find the Celebi.This source of information is always trustful and I reccoment you to use it.