Armchair general here, but if i were to guess israel's plan:

The northern part of Gaza is where the majority of rockets get launched, since they have geographical proximity to several israeli cities from there. IF israel annexes north gaza, that would already be very changing to the military situation. Hamas can obviously launch stuff from south gaza, but the geographical distance to israeli hotspots dramatically increases (by itself an obstacle), AND norh gaza can be transformed into an extended Iron Dome with several military facilities in place to act, not to mention that now Israel only has to watch half the terrain.

The heretofore events point to this possibiliy, since Israel gave the ultimatum to evacuate northern gaza, and south gaza for now seems to be spared from this. Of course, if Israel then eventually proceeds to colonize north gaza with new settlements (aka West Bank 2.0 electric bogaloo) , hamas has a new 'easy' target to hurl stuff into, but the military infrastructure in place will be much more impenetrable, and the local jews would be staunch sionists that accepted the risks and have high morale and preparations to deal with this, and not the mainstream israeli society.