Elongated Man in Multiversity

According to Grant Morrison's The Multiversity, at least a couple of versions of Ralph are still around in DC's multiverse.

The Multiversity is a limited series that explores multiple universes of the current continuity of DC Comics. In later years, the Elongated Man didn't even make cameos, however, that changed with The Multiversity Guidebook, the sixth issue of the series, which goes into detail of the entire multiverse and shows a list including most of its universes.

On Earth 44, as shown in page 57 of The Multiversity Guidebook, the equivalent of both the Justice League of America and the Metal Men is The Metal League. Created by Dr. Will Tornado, Gold Superman, Iron Batman, Platinum Wonder Woman, Nth Metal Hawkman, Lead Green Arrow, Mercury Flash and, yes, Tin Elongated Man.

They are all robot versions of the Justice League, the fun part is that is that the only human member is the equivalent of the only robot member of the actual league. 

Another version of the Elongated Man can be seen on Earth 26, which is the equivalent of what used to be "Earth C", during the early 80s. A world populated by anthropomorphic animals, including Captain Carrot and his amazing Zoo Crew, a superhero team. They are original characters rather than analogues of the Justice League, but it's worth noticing that one of the most prominent members, Rubberduck, has the exact powers of the Elongated Man and nicknames like "the ductile duck" or "the malleable mallard", equivalent to Ralph's "the ductile detective" and "the malleable marvel". 

In the old stories, the focus of the stories is Captain Carrot, and he is a comic book artist in his civilian identity. The title he draws is Just'a Lotta Animals, which features anthropomorphic animal versions of the Justice League of America. However, as it always happens in the DC multiverse, what is comic book fiction in one universe is reality in another. So, those Justice League parodies turned out to exist in their own universe, called Earth C-, and they even met Captain Carrot and his friends "The Zoo Crew" in some stories. 

In The Multiversity #2, during the crisis across the multiverse, the Zoo Crew is seen fighting Just'a Lotta Animals. Which, again includes a version of the Elongated Man, in this case, the Elon-Gator.

It wasn't specified if the new Just'a Lotta Animals and Zoo Crew live in different universes like they used to do (Earth C, and Earth C-). We only know that they have a fight on Earth-26, which belongs to the Zoo Crew, but no universe was listed as belonging to Just'a Lotta Animals. However, in the Multiversity series, 7 universes were left unknown, including Earth-25 and Earth-27. 

Most of the 52 universes include a version of the Justice League, commonly based on the 3 incarnations: the original "big 7", the new big 7 (with Cyborg replacing Martian Manhunter) and the satellite era. Clearly both the Metal League and Just'a Lotta Animals are based on the satellite era. However, it can also be argued that Elon-Gator was probably included to provide a visually interesting counterpart to the more recognizable Rubberduck.

Oddly enough, I don't remember a single Plastic Man in any Justice League analogue, despite the fact that Morrison himself made him a member. The exception might be Morphin' Man, a parody of the completely obscure Polyman, who is, in turn, a pastiche of both Elongated Man and Plastic Man.

I don't really know if the old realities are back after Convergence, (yet another miniseries in which characters from old or erased time lines get a second chance), but, so far, this year I have seen the return of the classic, pre-Crisis, Elongated Man, as well as the pre-Flashpoint one, the version from the Giffen-DeMatteis stories in Justice League 3000 (another unidentified universe), the Elon-Gator, Rubberduck, and Tin Elongated Man. Plus, on the main universe of DC Comics, Earth-0, there is a mysterious character called Ralph Dibny, despite the fact that he doesn't look anything like the real deal.

Some other universes like Earth-22 (Kingdom Come) are known to have a Ralph Dibny. Due to their connection with Juistice League Unlimited, in which he was a character, Earths 12 and 50 probably have other versions of him. It's also safe to assume that many of the other universes feature him, specially those with versions of all the characters of Earth-0 or Earth-1. 

All of this isn't really a comeback for Ralph Dibny, since he is not really part of a team with an ongoing title. However, at least his existence is acknowledged and he becomes available for any writer who might want to use him in upcoming stories.