How long till sly 4

How long until it is released? It was already released: February 5, 2013

How long between games? Sly Cooper 4 (Thieves in time) was released 8 years after Sly Cooper 3 (Honor Among Thieves)

The series so far includes:

Sly Cooper and the Thievius Raccoonus (2002)
Sly 2: Band of Thieves (2004)
Sly 3: Honor Among Thieves (2005)
The Sly Collection (a remastered release containing the first 3 games) (2010)
Sly Cooper: Thieves in Time (2013)

Sly 5 (in development, no public release date)