We currently have enough players that post often enough that the game is still riding on the edge of viable. If we lose more, I'll end the game and post the Big Picture reveal and take questions from the remaining players. I'd rather end it quick than let it drag and sputter, if it came to that. If things speed up again, then great.

I do have a metaplot flowchart in my head.

This is my first time GMing Amber, and I overestimated post speed and player retention. When deciding on my GM style, way back when, I didn't want to railroad, and I didn't want to rely on using Magnificent Bastard skills to try and lead players into doing things without them knowing I was doing it . But we had a big cast initially, so I figured I could weave bits of metaplot in and you clever and creative people would pursue enough threads of it that we'd be around the player convergence endgame about now. Feels more like we're halfway, so it did kind of work.

Options we have, if enough players feel strongly enough about any specific option:
1 - immediate end, big metaplot reveal, player Q&A session
2 - keep going. status quo.
3 - major revision and reboot (requires the most active players to actively be in on it, with the intent to actively pursue endgame). This one is complicated. I'd give a few spoilers away, you'd all get to revise your characters, and then it's New Game + with you retaining past character knowledge.

The biggest pitfall I see ahead is that I expect to graduate towards the end of summer and will be looking for a job then.