Whether Cummings was right or wrong to safeguard his family (and I still believe he was right), the way he went about it has certainly made it look wrong. He of all people must surely have known what the press would make of it. When doing something that is questionable, it is far better to be upfront about it, rather than attempt to hide it - you may still get shit thrown at you, but it will be far less if you are open about it.
Cummings has put Boris in an invidious position: if Boris does nothing, the next time he goes on telly and tells us how important it is that we all keep obeying the lockdown, he must surely know a sizeable proportion of the population will be going "yeh, right, one rule for us......".
Cummings has become a liability to maintaining the lockdown, but I think Boris regards him as essential to his political career. We are soon going to find out what is more important to Boris: the country or his career. The crunch is surely going to come when Boris next faces the press, or PMQs. I must admit that I had gone off the press questions after the daily briefings, but a couple recently have been particularly incisive and led to dramatic changes of government policy.
My bet is that Cummings will go, but then Boris will quietly reinstate him later on, as Cameron did with Coulson.