The Pokemon Global link will be down on June 5th to accommodate a renovation for B2W2.
It will include new pokemon for the Dream Isles, new decorations, as well as new areas that are easier to access/progress depending on Pokemon type.
The limit set before accessing the DW again will be reduced from 24 hours to 20 hours.
A new Report feature will be added that will keep track of your GBU and tournament rankings as well as your GTS trade history (a new GTS site will also be launched).
There are also special promotions planned for users who register a BW game as well as a B2W2 game, a B2W2 Tournament, C-Gear skins, etc, as well as the start of Season 6 of the GBU.
The news report also includes a warning that the update days will also be included in the rule for 100 consecutive days without play (if you don't play DW for over 100 days, your berries will be reduced to one, and turned into Dream Points, evidently).