There are plenty of environmental issues associated with desalination, it's not a get out of jail free card. Obviously energy use (and even if that energy comes from solar it's not completely free of consequences) but also the brine from desalination can cause significant local salinity issues which damages aquatic life.
All of those issues can be addressed with money, which is presumably not an issue because the original premise of this thread is that the rich will gladly pay the steep costs.
