So, what exactly was achieved? (Spoilers aplenty)
So, we know there's a cure. Edward and 'Elvis' are cured vampires. The blood substitute was successfully synthesized.
From what I gathered watching this, was that each time they cured a vampire, their companions descended on them in an orgy of death and blood, and then you generally end up with one living cured vampire. Which, in each scene in the movie, that cured vampire gets killed through conventional means.
So, basically, all the cured vampires besides Edward and Elvis are dead, and there's a working blood substitute.
Essentially, they succeeded in riding off into the sunset, having achieved absolutely nothing, other than Edward foolishly giving up immortality, and sooner or later, he's going to get killed along with Elvis, the only other cured vampire.
There's no real way for them to spread their cure, seeing as there's only two of them, and with a substitute, there's not going to be a frantic attack on them, and they wouldn't want to spread their cure via their own deaths anyway.
I can't really figure out what, if anything, they managed to really DO. Chances are, someone will report at what's found out, or perhaps Chris did in the interim between talking to Edward and later being killed (or even the whole thing was caught on security camera), Edward and Elvis will be marked as "shoot on sight, do not feed on" fugitives, and they'll likely be shot at some point in the near future, and vampire society will proceed as normal.