Can I ask why these are already released and what's going to happen when Death Plateau is eventually released?

No you couldn't that's just projectrs2006

The only way you could get them in 2006 was as a reward from the quest from troll stronghold and they weren't tradeable until around 2008 and that's when they became a drop from guards.

The Law talisman was originally a reward for completing the Troll Stronghold quest, which was required in order to craft law runes, was not tradeable and instead of a drop option, it had a destroy option. On 7 May 2008 Jagex issued an update for the law talisman, they stated the law talisman was not a good enough reward for such a difficult quest, and replaced the talisman reward with two Experience lamps, which give 10,000 experience each into any skill over level 30. They also made the talisman tradeable for Members, and removed the quest requirement in order to craft law runes. The initial price was 1500 coins. The talisman can now be obtained as a drop from the monsters mentioned, traded from another player, purchased at the runecrafting guild for 125 tokens, or purchased on the Grand Exchange; allowing a much larger number of players to enter the law altar to craft law runes or law run.

Thanks for this

r.i.p ::rickroll