Drones are not yet a viable alternative to the F-35 or other piloted fighter aircraft. While drone technology will surely meet and surpass the capabilities of piloted aircraft in the coming decades, it would be irresponsible of the Canadian government to delay a replacement of the CF-18s in anticipation of this eventuality. The CF-18s should be retired at the end of the life-cycle and replaced with piloted aircraft that can fulfill their existing roles and provide a comparable set of capabilities.
That said, the fact that drones will replace piloted aircraft in near future should lead the defence department and Canadian Forces to question whether a '5th generation' aircraft will truly be the best plane for Canada over the next 30 to 40 years. It is quite possible that advances in drone technology could make the F-35 an inferior fighter in only a couple of decades. This suggests that it may be wiser to acquire a less expensive 4th generation replacement for the CF-18s over the next decades, while investing in the development of a drone that could meet Canada's particular capability requirements over the longer term. This option should be considered, at the very least.