JimF-STL-MO:
will an enhancement or new version be released, for instance Rev4?
No, Arduino just sucks at keeping their products in stock. But never fear, the Chinese clone/counterfeit suppliers are always on their game and happy to pick up the slack.
JimF-STL-MO:
Can the UC3 Microcontrollers share the 8-bit libraries?
Well first of all you would need to find or make a hardware package to add support for those parts. I'm not aware of one.
After that you will find that some libraries can be used as-is but others are written for specific hardware and will need to be ported.