I think they clarified that some in a recent post Zid (see post by Bayohne here) but there is a limit to the number of instances being created--they just won't inform us how many. So while there may be some waiting the majority of big and active linkshells should be capable of running these dungeons simultaneously with little to no conflict (especially given server populations lately).

Though as you say, if we do run into these sorts of issues, a rotation schedule may be needed.