Unrecognized modifiers

In section 4.6.3 Modifiers:
"This allows implementations of this document to handle records with
modifiers that are defined in later versions."

Would later versions still have "v=spf1"?
If yes, then
        odd!
        Later versions should have different versions!

If no, then
        Why support something in spf1 that will only occur in spf2 or
beyond?

Thanks,
Guy


4.6.3  Modifiers

   Modifiers are key/value pairs that affect the evaluation of the
   check_host() function.

   The modifiers defined in this document ("redirect" and "exp") MAY
   appear anywhere in the record, but SHOULD appear at the end, after
   all mechanisms.  Ordering of these modifiers does not matter.  These
   modifiers MUST NOT appear in a record more than once each.  If they
   do, then check_host() exits with a result of "PermFail".

   Unrecognized modifiers MUST be ignored no matter where in a record,
   or how often.  This allows implementations of this document to handle
   records with modifiers that are defined in later versions.