I think first class tuples would be useful, I would imagine extension properties make it in as its been noted that they actually agreed on a specification for how to do it, just had to cut it for 4.0 in order to shipit.

 

Not sure about enumeration, a tuple is only a sequence in a syntactic sense, theres plenty of contexts for how you can iterate something, and I think there needs to be proper thought into what should be considered a native sequence to the language.. best bet is, does it really add anything? no, then its not worth introducing additional behavior.