Stefano,
I believe that once one has made a corporate choice for an email/calendaring platform based on many considerations, changing this platform will not happen any time soon. With regards to any change in platform in the future the question would be if the data is available and if it can be migrated. The level of difficulty to migrate, in my opinion, to a new future platform would not be a priority other then if it can be done and at what effort.
As with most of the GPL licensed applications, the data itself is stored based on GPL licensed applications. With all their benefits.
Other topics of interest would be the user experience and satisfaction, manageability and security and if applicable scalability, all based on a broader corporate strategy of business continuity.
Obviously NoTo is examining every angle on this and for a reason, probably that he is entrusted with this responsibility by his company. The only thing we should/can do is provide the best info we can based on SME Server. The choice what strategy to follow is up to the decision maker.
Hence the contribs.org wiki has no favourites and simply presents the possibilities. Whatever one may choose to do or select as an application or method, it's up to them.
Since NoTo introduced himself as a professional with good social, technical and management skills, I'm sure he will make the right choice for his company.
guest