The majority of OpenSky sites will not be "transitioned" to P25. I never bothered to do an exact count of how many of the P25 sites were also OpenSky sites, but I'm sure it's a pretty high percentage, along with some new sites in the mix. Overall it's still just a fraction of the total amount of OpenSky sites, however.
Having hit the cap of 150 sites per zone (RFSS), the state is in the process of acquiring and implementing a second zone controller (RFSS 2), so there are additional sites coming in the future. It will still pale in comparison to the total amount of OpenSky sites (1,000+)