I think they promised Workshop support with the 3rd DLC? Or did I dream?
Back to the progress update, as the talented developer he is, Steve knows he would be wise to release the first 'open beta' of AC# some 2 months before he goes on the road... Because from past experience, I know that there is approximately 0% chance that a game developer manages to find 100% of the bug of his game. We the players will find new ones!
The way modders have had to go about injecting things into the game, adding any meaningful official mod support through something like the Steam workshop would pretty much require a massive rewrite of the core game and how they're using Unity.... certainly not impossible but given their official stance is that they don't support modding in their game at all, it's really not going to happen.
On the topic of guesstimates on the most appropriate lead up time for C# distribution, even if Steve were to just focus on wrapping up the known major issues over the next week or two, decide diplomacy can wait for getting feedback on the rest of the core of the game and release now, he'd likely still have new bug reports and fringe case issues coming in this time next year on that exact same build, so trying to assign any kind of meaningful lead-up time for "When is the best time to release to get reports back on additional issues" before his mentioned downtime is like trying to predict the length of a piece of string needed for a task before you know what the task is nor the quality of the string itself.
There really isn't a ideal appropriate lead-up time before March, it all really depends how Steve wants to approach things, how much time he'd want to spend investigating submit issues and how much he'd like to just carry on with his existing plans and then loop back around for fringe case issues later.
In one scenario it would make all the sense in the world for Steve to intentionally not release anything openly until March, throw it out and then step away from it all for a few weeks to allow the reports, discussion of shared experiences of the same issue (or not) and potential community solutions/workarounds to happen, then once back at some point go through the range of reported issues, weed out the ones that will resolve themselves naturally once already planned work is completed, or issues that aren't actually what the person reporting says they are. Then assign the rest into severity categories, amend existing development focus accordingly and then shut out additional input on issues until the next significant release milestone and repeat the process all over again... Release. -> Step back. -> Weed out. -> Assign issues. -> Adjust schedule. -> Develop. <--> Repeat loop.
From a personal interest standpoint I'd hate to see that happen as I am busting at the bit to dive into the C# build and poke around, and the idea of there being nothing tangible for another half a year almost would really be a huge shame but I can understand if Steve were to take such a approach, especially with how Aurora development is being handled and the ever shifting real life demands.
Really only Steve knows what kind of lead up (or no lead up at all) would work best around known real life plans given how he wants to approach the project, hence my original question trying to ascertain what Steve had in mind in terms of what would qualify as an open feedback viable state for C#.
From the answer given, it seems in terms of the state of the project itself, C# Aurora could pretty much be released today and it would perform decently against the current VB release (if not already better) for most users outside of Diplomacy (The severity of Diplomacy being missing I guess is a question of personal opinion lol) and begin getting feedback by this evening. But that increase in forum noise may not be appropriate for the decided approach, especially with known issues likely being reported over and over again even if Steve were to include disclaimer links everywhere in large font to a list of known issue alongside the release.... perhaps only releasing when there is a more assured real life period of downtime and being able to remove himself for a period of time after the release is seen as important with whatever way Steve would prefer to approach things.
Or maybe there are a thousand other factors that are influencing when the most appropriate time to push anything public out is, I wouldn't at all be surprised if Steve hasn't already picked out a series of long term forum posters or individuals he knows in real life and even has some closed group feedback collection going on, and if that's the case then the net gain from any kind of public release suddenly becomes massively depreciated, would certainly make sense for him to have gone down that route as that approach does significantly improve the quality of feedback and ability to respond to it directly for situations like how Aurora is being developed.