According to an article on Mainichi JP, Gackt has changed his name to GACKT. The caption under his photo says:
tooka kara namae hyouki wo subete oomoji no arufabetto ni kaeta GACKT-san
Which means, “GACKT, who changed the way his name is written to all caps since the 10th.” So, get friendly with that caps lock key y’all! Click to see the article on Mainichi JP: HERE.
If I’m not mistaken, it’s actually common for Japanese bands/musicians to make such slight alterations to their names when they achieve major milestones, or anticipate that they will. I read in Josephine Yun’s book jrock, ink. that X JAPAN added the “JAPAN” in anticipation of an international debut, and that Kagrra, added the comma to their name for the release of their major label debut album. So, this all caps business is about marking his 10 years as a soloist, not about being a diva or anything like that.