No, but the Dead Three are still around

Several gods died during the Time of Troubles, notably including the Dead Three: Bane, god of tyranny, Bhaal, god of murder, and Myrkul, god of death. However, gods are difficult to destroy in the Forgotten Realms, and all three of the dead gods have devised schemes to return to power. Bane’s plot was successful, and he has supplanted the Godson who inherited his portfolio. Bhaal’s scheme was the main plot of the Baldur’s Gate video games. Myrkul appeared in the Neverwinter Nights video games, but so far he still appears to be a dead god, rather than a god of death.

Therefore, the entries for Bhaal and Myrkul currently appear to be there primarily for historical interest, for DMs who want to use them in the past of the Realms, or who want to feature their schemes to return to power. They do not indicate that Kelemvor has lost or changed his portfolio – yet.

The holy avenger was officially part of the Forgotten Realms since the beginning.

The official beginning of the Realms in a game publishing sense¹ starts in 1987 with the Forgotten Realms Campaign Set—the “Grey Box”—published for first edition AD&D. By that point the holy avenger was already an integral part of AD&D, appearing in the DMG (1979) on page 165.

Note that Supplement 1: Greyhawk is a 1975 supplement for the earlier, original D&D game (dubbed “original D&D” or “0e” (zero-e, oh-e)) published in a box of three stapled booklets in 1974. The holy avenger by any name was a well established part of the game before AD&D or the Forgotten Realms were even conceived of as publishing products at TSR.

The 1987 edition of the Realms predates the idea of AD&D edition changes and the accompanying cataclysms in the Realms. Those were later inventions by minds at TSR after Gygax had been forced out. This makes the holy avenger part of the baseline Realms from which every edition change and cataclysm later derived.

So for the purpose of tracing the origin of the type of magic sword, it’s integral to the Realms, and its AD&D description is the baseline version, before any Realms events that changed how magic works.

1. A note on when official-ness applies to the Forgotten Realms. The origin of the Forgotten Realms predates D&D entirely, circa 1967, as it was an invention of Ed Greenwood’s childhood imagination before he encountered D&D. It’s not possible that anything derived directly from the D&D holy avenger was part of this pre-D&D conception of the Realms. Even when Greenwood was publishing his home game’s details in Dragon articles, it wasn’t “official” at that point even if his home game likely had a holy avenger at least in their rulebooks, as Greenwood’s articles were just a fan sharing his ideas and Dragon at that time often published fan/homebrew material that wasn’t endorsed as “official”. As Greenwood wrote more articles, the line between official and fan eventually blurred, to the point that TSR bought the Realms and published a novel and the Campaign Set in 1987. This answer uses that year as the most meaningful and clear beginning to the “official” Realms. The very first official publication was actually the novel Darkwalker on Moonshae, but only by a month since it was written in tandem with the official campaign set, so that doesn't impact the 1987 start-date.