Is it safe to connect dish washers and laundry machines to hot water?
The problems are twofold: too hot for some things and too cold to save much. 

A modern washing machine uses surprisingly little water (though top-loaders still use quite a lot). By the time the hot has come through, most front loaders will already be full. At this point the water just cools down in the pipes wasting heat, while the machine's heater has to run. Many programs use cold water for at least the first rinse.  If you connect only a hot line you waste more heat at this step. By the final rinse the water will be quite hot. But when you want a cool wash for delicate clothes, the final rinse will still be hot (even if all previous steps aren't) thus ruining expensive clothes. 

Some machines may also get confused and refuse to run if the incoming water (expected to be cold) is above the  program's setpoint. 

Cold feed only is the norm in Europe, specifically to save energy. The only exception would be if hot water is plentiful but electricity is expensive. This is rare. 

The situation is similar for dishwashers. 

To answer your title: no, or at least probably not given that it's cold feed only