Hey, usually I'm the salty one?
No. It has been established that Katastrophe is the one. You can be the substitute if you want, though :p
Getting a new crowd into RMU will be difficult before the core books have been released, no question about that. However, any players with experience from previous versions could start playing any time they like. It might not be a perfect match, but you can use creatures from any of the previous versions without breaking anything. You can even use Shadow World with minimal effort.
Actually, you need effort to play Shadow World even with the existing RM system(s). I'm not exactly sure why, but it always seems like SW was designed with another system in mind, or, more likely, it was designed *without* a system in mind and the system was tacked on afterwards. I know it's probably not true, but it *feels* like it is.
Now, ofc everyone would like a more rapid release schedule, but you can still play while waiting.
I suspect Shadow World will be more difficult though. Disregarding all the red tape, licensing, IP, etc. Relaunching Shadow World for RMU would require a lot of work.
Depends on what you really want to do. A RMU-compatible Master Atlas would probably go a long way. You usually have all the basics in it, including sample monster and NPC stats, racial stats, timeline, world overview, herbs, linguistic tips...).
There are quite frankly parts of it that are an absolute mess. I love Shadow World, but it's far beyond just simple quirks. The Unlife is a core concept for example, and I wonder if it's even possible to use it RAW in any of the previous editions? It appears to require some significant house ruling just to get it playable?
I suspect it was not meant to be "playable". It was meant to be the bogeyman. But even with that caveat, it is a mess.
With RMU there are parts that wouldn't be possible even with house rules (unless you go deep down the rabbit hole). So, serious re-writing and fixing needed.
I personally wonder if ICE would be prepared to do what's needed? Rolling out a reprint with new stats is one thing, but sorting out the mess and rewriting the books for the new system is a very different matter.
I think they once said that they would be open to resuming the product line if they could find one or more people who had the skills, time, and passion to act as active caretakers (read: line editors). SW, especially during its heydays prior to TKA resuming control over the IP, suffered from an "anything goes as long as it uses a couple of key words" line editing policy, which translated into products that were of subpar quality and only marginally consistent with Shadow World as a whole. The later products (from Emer I onwards) were done with TKA at the helm and it showed - there was a consistency in the writing and the underlying setup that was clearly missing before. I did not agree with every choice TKA made (quite the contrary),, but the effort to go back to a consistent product line showed.
that's what is needed right now for SW: one or more persons who are very knowledgeable about Shadow World, have some time on their hands to work on a full update, and have design and writing skills - and, if more than one person, who agree on the foundations of the setting and on the direction it should take.
Let's just say, I'm not optimistic that they will find those people any time soon.