Concerto EPI SDRAM recommendations

My customer is designing with Concerto and is asking for recommendations of external SDRAM.  Question #1:  What single data rate SDRAM is used on the Concerto EVM?

According the Concerto Reference Manual (page 1335), up 50MHz SDRAM can be used.  Question #2:  But isn't 50MHz SDR a bit short sighted due to the probable lack of future availability of SDRAM?  Meaning how do I convince my customer that this isn't a problem and 50MHz SDRAM will still be available 3-5 years from now?

Thank you.