The reality of the situation is that moratrs are going to be around for a long time to come. They are cheap, lightweight, fast to set up and get into action, plus they can be deployed within eyeball of the enemy. And, not to be dismissed lightly either, pound for pound they offer a bigger bang and greater lethality than 'conventional' artillery rounds.
Mortar rounds may include airburst, burrowing (to explodes several seconds after impact) and regular impact. They may include sub-munitions, such as a bomblets, top down anti-armour rockets, micro-bot cloud, drones, minelets, ECM They may also have 'smart' munitions that can search for a particular target signature - a type of tank, infantry, or even an individual.
With the increase in mortar round detection and defence systems coming into play today, mortar rounds may have to be 'stealthed' so they are blind to the enemy Grid
Even in the 70's mortar locating radar systems could backtrack mortar rounds to locate the firing position. Future technology will only make it easier, even for the individual infantryman and allow countermeasures to respond immediately..
Mortars may well become like LAW's or other disposable rocket systems. A futuristic mortar could be a single shot or magazine fed weapon. Automated - on the Grid and highly 'disposable'.
A field of 'remote' automated mortar tubes could be deployed by the infantry or even by drop capsule. The Grid or even the infantry themselves could transmit fire support orders to the mortar's on board intelligence chip which makes the necessary calculations and fires the number and type of tubes necessary. Any enemy counter-measures simply target a group of now useless tubes.
In a hostile aerospace environment it could be that the scenario is for a small group to iniltrate enemy positions, set up a mortar - manned (for protection) or remote, and then launch a smart munition on a laser painted enemy facility or personage at the correct moment.