We present an observability model that can be used to predict expected magnitudes for young planets embedded in transition disks, still affected by extinction due to material in the disk. We focus on Jupiter-size planets at a late stage of their formation when the planet has carved a deep gap in the gas and dust distribution and the disk could be transparent to the planet flux at certain wavelengths. The expected magnitude at typically observed bands in the IR is estimated by means of three-dimensional hydrodynamical models, performed for several planet masses. Observed fluxes are obtained by combining these models to giant planet evolutionary models for typical extinction properties of the material. We find the detectability of the embedded planets with masses approximately 1-2Mjup to be strongly dependent on the assumed disc masses and on the wavelength considered. For most cases these planets would be hard to observe at the J-, H- and K-bands. On the other hand planets of masses approaching 5Mjup are always detectable. We derive observability curves that we then apply to the transition disks around CQ Tau and TW Hya