$SWITCH$ macro has been deprecated? Then what is the suggested alternative?

SwitchMacro has been replaced with TemplateSwitchMacro. The $SWITCH@ alias has been preserved.

Vaclav

Thanks, Vaclav.
Maybe this should be migrated by 3.0 -> 3.1 migration assistant?

It's not migrated automatically as both are functional, they behave the same unless switch got parameters (which is rare cases, as it's functionality added in 3.1), for switch with parameters only new SWITCH macro would work. It's left to language designer to decide when to migrate (though I'd migrate asap, as there's plan to drop legacy switches in 3.2). There's intention you can use to change old SWITCH instance to new on a one by one basis, or use "migrate all" action to fix all instances in workspace (Tools->Scripts->Migrations->MPS 3.1->Update SWITCH macro to support parameters).