If you're setting a game during the Cuban Missile Crisis, look through a library. find out what people were wearing, what other issues were in the news, how houses were furnished, what cars were being...
I'm rather pleased with the new manuals. I see Inform now as a gauche young adult, having got past the stage of growing out of his shoes every few months.
For a fortnight nobody at all emailed me, or posted a follow-up. Doesn't anyone care, I thought? It turned out my newsreader was broken, and hadn't posted at all.
If pushed, though, I'd say that the next stage will be reached when it it's no longer true that about 75% of the best games were written in 1980's on the way to that.
Writing a really general parser is a major but different undertaking, by far the hardest points being sensitivity to context and resolution of ambiguity.
This means keeping many trails open at once, inevitably requiring a fairly 'parallel' plot. This plot should be discovered rather than announced, so show, don't tell.
What I would pay much more attention to are the few points where the player can inadvertently make a career decision. Most players end up back-tracking, though some actually enjoy this.
The 'interactive fiction' format hasn't changed in any fundamental way since the early 1970s, in the same way that the format of the novel hasn't since 1700.
The time has mainly gone on getting Inform into a decent shape for public use. I suppose the plot of 'Curses' makes a sequel conceivable when compared with, say, the plot of 'Hamlet' but none is...
Eventually I found it had been working all along-but didn't show anything on screen until it had the first full page of text. I inserted 30 new lines, and suddenly my toy said 'hEllO woRlD'. An hour...