They are trying to decentralize their operation so it will be more difficult to take down the piratebay.

I do not see this as good news. tpb works. If it ain't broke, don't go mucking about trying to fix it. If they think they can maintain control without ownership they are seriously delusional. A company with a stock symbol is beholden to its stock price, not idealism.

TPB is down. Related to sell-out or just massive traffic due to the news?

Neither, actually; according to http://torrentfreak.com/the-pirate-bay-closes-its-tracker-re..., Pirate Bay is closing its tracker and will some kind of third party tracker in place.