Wish I could get down to one camera, but even though I could get by with just one, I feel that I like taking pictures more in nature with the Hasselblad or 6x6 pinhole, and people photography I do better with 35mm. The prints seem to come together better for me this way.
Use as many cameras as you want, but don't let the camera get in the way. Any camera that doesn't feel natural to me to use gets axed. Same for too many cameras of the same kind.
35mm SLR - Qty 2 - Pentax KX with various prime lenses
35mm RF - Qty 1 - Leica M2 with various lenses
120 6x6 - Qty 1 - Hasselblad 500 with three lenses (want one more body for backup)
120 6x6 - Qty 1 - Zero Image 2000
I own a Spotmatic and a few other loose ends of cameras, but none that I really use anymore, because they fill no function that isn't already filled.