I'm sorta the other way. I have a 9mm Pro, three M&P 9mm's (personal gun, issued gun, and range issued gun), and a 9C. I will buy a Shield as soon as it gets approved, but I will definitely keep the 9C.
I have shot a little less than a thousand rounds through our test Shield so I'm not unfamiliar with the pistol. The 9C is my main carry gun, and will stay that way. With the 9C and one spare full-size magazine I have 30rds on me. With the Shield and one mag, I'd have 15 - 16. There are times, however, that the 9C is still a bit on the large side (Church, around the house, etc.) and the Shield will fit that role perfectly.
So yes, I think there is a place for all three versions.