If this https://en.wikipedia.org/wiki/Federal_Express_Flight_705 didn't end deadheading, this event won't. Whether the airlines are looking for an excuse to end deadheading I don't know.
Doubly not going to be happy if they have to live in bases in California and pay income taxes there instead of commuting in from no-income-tax states like Washington.
The doors&locks are really good now. So good you can even lock out your co-pilot while they stop in the bathroom… (an argument in favour of having a 3rd deadheading pilot next to the others)
In response to the incident and the circumstances of the co-pilot's involvement, aviation authorities in some countries implemented new regulations that require the presence of two authorised personnel in the cockpit at all times.
So if a pilot has to visit the lavatory, a flight attendant or some other qualified person has to replace the pilot on the flight deck (not in actual duty of course, just not leaving a single person alone there).