Gosho's death is closer than Conan ending
He is 56 years old. He can go for another 8-10 years, if he is allowed to stay healthy.
If you need a break that long just to advance an inkling of the plot
No, needs that long a break to prepare all the upcoming chapter storyboard of the new case at once (so, 4-5 chapters worth of storyboards), color drawings for the Volume 97 in Japan, his reveal poster for the Movie 24 reveal in November/December and this is also most likely around time when he is drawing his animation keyframes for the upcoming movie.
He took a long break like this last year too around this time. The other breaks between then were just the usual 4 week breaks, which are similar to what some other authors take to prepare new chapters. But since the long break is now a pattern, it would appear that his usual involvement in the movie production is the reason for this. Considering he previously was doing all of this while taking no breaks at all, year after year, it is logical that won't stop doing it - but it is not 1999 anymore, and if needs these publication breaks (just publication breaks, not "break" in general, since he works during that time) to stay healthy OR if the editorial department mandates those breaks (after all, the last health hiatus between December 2017 and April 2018 wasn't his idea, his editor forced him to do it), then I'm okay with that.
and mom survived, but not the adopted son of the mom
Kouji is not the adopted son of Mary, Shukichi was most likely the adopted son of the Haneda family.
Also, yeah, APTX is lethal, Amanda Hughes died to it, as well as all those other people on the APTX victim list.