Yes, you can always find another Leica M body.
The Zeiss Ikon is a beautiful little camera, and the viewfinder is astonishing. It's a joy to look through. I found it difficult to "jump" into being on-axis so I could see the rangefinder patch but I'm sure you get used to getting to it really quickly.
The body is significantly lighter, though. One of the things I love about the M4 is its weight--twice as heavy at 600 grams (ZI is 300g). The M4-2 is 525g; lighter than the M4 but still significantly heavier than the ZI. For me, it's important because I feel that I can hold slow shutter speeds steadier.
I almost bought a ZI myself, but I ended up picking up a selection of M bodies instead. It was a better decision for me, but for the right user, I think the ZI would be ideal. I hope that's you!