As far as I know there is no incompatibilities. Actually the software doesn't use tricks or weird system stuff. As a result it should be compatible with a lot of future Mac OS versions. Anyway I will be there to fix any problem if necessary.
Yes, that will be done in a near future. (Note however Cocoa is not a language but an API - Right now we still use the Carbon API. As soon as possible we will switch to Cocoa)