Drop support for legacy sh - assume bash is always present?

[joeytwiddle]

I started writing jsh on a Solaris machine which at the time had no bash installed.

Wanting to support any other people in the same situation, I have kept many jsh's script compatible with #!/bin/sh, only specifying #!/bin/bash when it was needed.

However it's 2014 now, so I wonder:

Are there any systems still in use where a POSIX sh is available but bash is not?

If the answer is no, then I should start using advanced bash features wherever they are useful, rather than retaining legacy compatibility.