Question about future PHP capabilities

readonly_current.php

<?php

interface Entity {
	public Uuid $id { get; }
}

readonly class Thing implements Entity {
	public Uuid $id;

	public function __construct(
		public string $key
	) {
		$this->id = Utils::makeThingId($key);
	}
}

readonly_virtual.php

<?php

interface Entity {
	public Uuid $id { get; }
}

readonly class Thing implements Entity {
	public function __construct(
		public string $key
	) {}
	
	public Uuid $id {
		get => Utils::makeThingId($this->key);
	}
}