725 For what it's worth, the ISO has implemented the new 13-digit ISBN standard as of more or less right now.
The system that has served since the 1960's, 10 digits (9 plus a check digit) can identify up to one billion publications. The system isn't taxed, but that is possible in the future, especially in as much as, like many such systems, segments of it are allocated for special uses. In the interests of solving a problem before it occurs, the ISO has jumped out in front of it.
The basic difference to the layman is that the ISBN will have a new three digit prefix. But those who maintain databases and even book designers should be well aware of it by now and, if you aren't...well, here you go.
This system should provide enough numbering space that they shouldn't have to fix it until after we establish our Alpha Centauri colony, I think.
ISO has an FAQ about ISBN visibile HERE.