It looks like Diabolik survived at the end, but is encased in gold and is finished. However, we know that his suit can withstand the temperature of molten gold. The government is going to want its gold back, meaning it'll have to remove it from Diabolik's body...by melting it. So, when the gold has been melted off, he'll be alive and free from imprisonment. And here we go again...
Not really. They can easily shoot him through the gold, or just let him stay there 'till he starves to death.
Diabolik, when out of ammo, uses emeralds as improvised bullets, shoots another man without gunpowder or shells and somehow makes sure every emerald-bullet hits and does not pass through his body while doing so or without shattering the emeralds in the process. Then we are to assume that the emeralds weren't noticed by the medical examiner (but hilariously bothered to count the bulletholes so that Ginko could get a clue later). And again somehow the emeralds weren't destroyed during the cremation of the man's body and could easily be recovered from his ashes by Diabolik later.
And that the bullets wouldn't be removed prior to cremation.
We see Eva gets arrested at the end and Diabolik still alive, but believed to be dead. However, we saw at the beginning that the Prime Minister and Parliment had re-instated the death penalty in response to Diabolik. Seeing as Eva's involvement in Diabolik's crimes is clear beyond a doubt, then even if Diabolik escapes he may find that Eva has been executed. This would probably drive Diabolik insane with grief and he would then stop stealing or pranking to instead engage in terrorist antics closer to V from V for Vendetta.
Then again, it seems that Ginko is sympathetic towards Eva. It's possible he'd intervene to spare her from such a punishment, since Diabolik himself was responsible for the major crimes.
Going by the comic books, he'll do not: the only reason she was never sentenced to death is that the one time they kept her in long enough to try her Diabolik managed to make it look she was an Unwitting Pawn (he needed time to break her out). And if she believes Diabolik is dead, she'll make a deal with the police to make sure she's executed.
Frige Relief: she knows he's not dead (remember, he clearly revealed himself to her at the last minute), so she might be able to hold out.
And the full-length cut isn't really any better. The only other person explicitly shown to survive the incident is Ginko's sidekick Sgt. Danek (the young guy in the brown tweed suit), and the un-MSTed version indicates that he had departed the train before the bridge bombing, in order to go chasing after Diabolik.