We don't know if Vegapunk can read the poneglyphs, maybe he used what was written in the books of Ohara for his digging but it's no the same as being able to read the road ponegylphs
I mean Laffite might do it next chapter, Blackbeard Pirates haven't left the island yet
Unless Robin somehow learned to read Poneglyphs from a source outside of Ohara after Ohara's destruction, Robin learned to read Poneglyphs from spying on the researchers of Ohara's basement using her powers, against their wishes.
Robin was an amateur archeologist with a bodypart-producing Devil Fruit, Vegapunk is the smartest being in the verse with the Brain Devil Fruit.
If Robin learned to decipher Poneglyphs from the same info Vegapunk received, but Vegapunk can't decipher Poneglyphs, it doesn't make any sense IMO.
Regarding Laffitte, since he can fly, he wouldn't need Augur's help leaving the island, either, Laffitte would just need Augur to teleport him past the laser grid. Then, Laffitte can turn off the Frontier Dome lasers from inside, and fly out with York and the Seraphim using the magic-flying-boots York and the Seraphim have.
Still wondering where the hell the Blackbeard Pirates parked their ship, though. Technically Augur could teleport it inland to hide it, I guess. It's possible Egghead is inbetween Winner's Island and Hachinosu, and that Teach is heading this way either way. Maybe Augur teleported here, and Teach is on the way to pick them up?