I think the P225 has a very dedicated following among SIG lovers - maybe not as big as the P228, but sizable. To me and many SIG fans, the P225 has the best ergonomics of any SIG. The P228 grip may only be slightly thicker than the P225 one, but the shape and design makes the P225 feel significantly better handling for many.
As mentioned before the new P225 is supposed to have a stainless steel slide and there will be an all stainless version. The P225 is a rather large gun for its 8rd capacity especially compared to more modern designs, but I think this re-issue is intended more as a range gun, or for "collecting", not necessarily intended for carry. I suspect it will be a limited run, but I could be wrong.
However, the new P225 is rumored to be based on the P39 frame, and if that is the case, then I will probably not be interested.