According to the upcoming issue of Magazine Special, a new Tsubasa: RESERVoir CHRoNiCLE manga will be serialized in the magazine. Similar to how the original series was connected to xxxHolic, the new manga series will be tied to the sequel, xxxHOLiC:_Rei, which CLAMP is currently publishing. The series will debut on August 20th in the August issue of Magazine Special.

Tsubasa: RESERVoir CHRoNiCLE was serialized in Kondansha's Weekly Shounen Magazine between May 2003 and October 2009. xxxHolic was serialized in Bessatsu Shounen Magazine from February 2003 to 2011, and its sequel began serialization in Weekly Young Magazine in March 2013.

Source: ANN


Update June 21
According to a recent blog post on CLAMP-NET.com, the Tsubasa sequel will be published for a short period of time. The title is Tsubasa: Another Story.

Source: CLAMP-NET.com


Update July 7
According to a scan from the 32nd issue of Young Magazine, xxxHOLiC: Rei will go on hiatus after the latest chapter to connect with the start of Tsubasa Another Story. In addition, the official title has been announced to be Tsubasa: WoRLD CHRoNiCLE - Nirai Kanai-hen.

Source: ANN, Natalie

Discussion continues from here.

Tsubasa: WoRLD CHRoNiCLE - Nirai Kanai-hen on MAL