There have been 2 types of spirits released since WotG that show that SE no longer feels the old spirits are worthy opponents, but no evidence that these spirits will be released to SMN.

1) The "copycat" fiends in Campaign. These spirits cast whatever spell the SMN casts. This would be a great addition, if SMN had any real spells besides summons. Perhaps if they allowed Addendum: Dark Arts to expand past the subjob level, this would be acceptible.

2) The multi-element spirits in Abyssea. I don't see these spirits being any better than the junk we have.

The problem is that spirits are flawed from the ground up. You can't magically make them effective.