This is not really a matter of priority. I am not sure 100% but I guess IC would work better with ARC/ORC.
You can always follow the development of IC by looking at issues on github
<https://github.com/nim-lang/Nim/issues?q=is%3Aissue+is%3Aopen+incremental+compilation>
or
<https://github.com/nim-lang/Nim/issues?q=is%3Aissue+label3A%22Incremental+Compilation%22>+
P.S: don't know why this is written in bold.
