I haven't entertained this idea as I absolutely adore my IQ1, I think they are rare enough to enjoy the 'uniqueness' feel, they are nippy and great fun to drive.
The Smart looks very very similar, but owning one of the original Smarts years ago, I find them very dated and small, not been inside a new looking one.
Every other car I see are Fiat 500's and they're as common as dog s@!7, so I won't be choosing them.
I don't think there is anything as quirky, attractive or modifiable as the IQ around to consider anything as a suitable replacement.
I hope that fateful day is many, many years ahead. I for one am keeping my IQ and enjoying it for a VERY long time.
Matt