IN16 will be upgraded within the ILL Millenium program. We present briefly the concepts which will ensure that the extremely successful backscattering spectrometer IN16 maintains its leading position. The most important component is a phase space transformation (PST) chopper for which the spectrometer has to be placed on an end-of-guide position. We summarize first simulation results for the two guide positions in question, based on simulations of the source, guide, selector, focusing guide, PST and Doppler monochromator arrangement.