In CNC milling can laser, now, practically replace normal machine heads for milling larger items? If not what?

CNC Milling Machines need traditional heads, and cutter operations. especially for large jobs.

However, lasers are great for smaller jobs, and touch-up operations. As of this point, nothing is out-their to replace a normally(Traditional) CNC Head.

Lasers will not replace standard milling tools. The problem with lasers is that they keep going until they hit something.

If your part had two pieces separated by a gap, and you needed to machine a hole in one of the pieces, a drill bit would do this easily without touching the second piece.

However, a laser would begin cutting through the first piece, and once the hole was made, it would immediately begin cutting through the second piece if the beam was not turned off immediately. At the least, you'd get some scarring on the second piece.