I'd suggest you wait because Canon released news earlier this summer about a new stabilisation system and they said it would be especially good in macro lens so the rumor is they will replace the 100mm by the end of the year.

I'm not sure it's an upgrade either, maybe with the new stabilization, maybe.  They are different lenses the 100mm is very sharp much lighter and faster so unless you need the extra reach I think stay with the 100mm.