I presume that this will be well sorted by 2008, seeing that, from what Sirena say on their website, they should meet all the criteria by then. This "International Consortium" should have plenty built by then.
Anyway, what about Wouter's point ? ISAF Class recognition cannot have anything to do with the decision
See the excerpt from the Sirena site below.
http://www.sirena-voile.com/en/news/news.html

" ISAF COUNCIL VOTES IN FAVOR OF THE SL16 »


Following the recommandation of FEB 6, 2005, the ISAF ( International Sailing Federation ) council* has selected the SL16 for Youth Worlds (submission 086-05. www.sailing.org ).
*the council includes 40 members from all over the world of sailing.
THE SL16, a modern catamaran designed by Yves Loday, and developped with SIRENA, brings performance and innovation in the world of multihulls.
Indeed the SL16 is very fast going on the wind ,or windfree with the spinnaker, or long distance ( 2004, 2005, regattas).
The SL16 is a marketing success supported by an international consortium:
-this “ one design catamaran” already selected by the French Sailing Federation (model 15.5) is build worldwide in UK , USA, ASIA, and FRANCE in view to cover the requirements of each continent.
- the motivation of the International , and MNA’s Class Associations shows the interest around the SL16. (www.slica16.org) .
It will take a few months to allow our licenced builders and the sailors to be at full speed with the SL16, although all the owners of a SL15.5 are able to upgrade it with a SL16 Kit.
More news very soon...