If they were to decide to move to a US exchange, nothing really happens with the shares now trading on the NYSE Euronext.
It only means that the shares would be bought and sold via the Nasdaq or NYSE in the U.S. There is no change of share count- the exact same shares/number of shares would be bought/sold thru a different exchange.
This CEO has a background in finance and he also owns 65% of the shares, so I think that's why he seems very open to the possibility of having the shares trade on a US exchange.
That's why he said: "The potential of 3D printing is almost unknown on European stock market. If this was to last for long, we could envisage any financial strategy that enables us to reach the huge financial leverage our competitors have."
So I take that as if the shares don't appreciate in value to where he believes they should as compared to US listed stocks like SSYS, DDD, XONE that he'll move over to a US exchange.