I said this earlier, something is probably going to happen to Duel next year to celebrate its 30th anniversary. We can evidently see this on the ride as all the original HH props are still working but a good majority of the post 2002 props are starting to fail, like the bust before the Grand Hall, the zombies before the Giant spider, and the finale.
If I had to guess if they are to do anything for it next year, it'll be,
A) The least likely (Unfortunately) will be Duel going back to the HH with a HUGE retrofit to resemble its opening year With the help of John and remaining Spark Groups workers.
B) Duel is going to have a massive refurb with fixed props, trommel working, lighting, and new merchandise of Duel and the HH.
And C) They'll invite John Warldey and Former Spark Group employers to celebrate it and have a meeting with guests outside the Facade.
I doubt they'd permanently close it next year as we've heard nothing of the sort so far from Merlin. They are very aware it's a well beloved classic, well what's left of it that is. If they were to close it, they would probably give us a 6-9 month warning on their Social media. But for now, nothing has been announced yet, if anything was to Happen to Duel, we'd most likely have some official info by late Closed Season.