Mode S to become requirement?

There has been talk of making Mode S a requirement sometime in the future.
Our transponder is giving trouble again. Does it make any sense to consider
putting in a Mode S transponder now, if we have to replace ours? We can get
a yellow-tagged Mode C transponder or even a new exchange from Narco
reasonably cheaply (for avionics, that is), but will it become a boat anchor
when (if?) Mode S becomes a requirement. Thoughts?

Thanks

--
Bob (Chief Pilot, White Knuckle Airways)

I don't have to like Bush and Cheney (Or Kerry, for that matter) to love
America