At its 25^{th} meeting (November 2014) the CGPM adopted a Resolution on the future revision of the International System of Units. This Resolution built on the CGPM’s previous Resolution (2011), which took note of the CIPM’s intention to propose a revision of the SI and set out a detailed roadmap towards the future changes.

In the revised SI four of the SI base units – namely the kilogram, the ampere, the kelvin and the mole – will be redefined in terms of constants; the new definitions will be based on fixed numerical values of the Planck constant (*h*), the elementary charge (*e*), the Boltzmann constant (*k _{B}*), and the Avogadro constant (

*N*), respectively. Further, the definitions of all seven base units of the SI will also be uniformly expressed using the explicit-constant formulation, and specific

_{A}*mises en pratique*will be drawn up to explain the realization of the definitions of each of the base units in a practical way.

(source BIPM)

More information on the BIPM website.