In fact they are down since Meruru, the decline for Shallie may be worrying though (its LTD number could be a bit higher, we're still waiting for the Top 1000 2014)
Arland Trilogy
PS3 Atelier Rorona: The Alchemist of Arland 47,456 / 91,639 Gust 2009-06-25
PS3 Atelier Totori: The Adventurer of Arland 72,836 / 133,495 Gust 2010-06-24
PS3 Atelier Meruru: The Apprentice of Arland 100,722 / 144,998 Gust 2011-06-23
Dusk Trilogy
PS3 Atelier Ayesha: The Alchemist of Dusk 75,874 / 102,145 Gust 2012-06-28
PS3 Atelier Escha & Logy: Alchemists of Dusk Sky 58,169 / 91,538 Gust 2013-06-27
PS3 Atelier Shallie: Alchemists of the Dusk Sea 54,554 / 72,811 Gust 2014-07-17
Similarly the Vita ports' sales are declining too (E&L should be a bit higher than 20k,
Dengeki had it at 22 last time it charted)
PSV Atelier Totori Plus: The Adventurer of Arland 30,956 / 57,000 Gust 2012-11-29
PSV Atelier Meruru Plus: The Apprentice of Arland 24,996 / 39,506 Gust 2013-03-20
PSV Atelier Escha & Logy Plus: Alchemists of the Dusk Sky 16,612 / 19,877 Koei Tecmo 2015-01-22