Wow, I didn't realize the software fix hadn't been rolled out prior to yesterday's crash. Yikes. Also count me among those who went through the rest of this year's (already booked) flights this morning to ensure I'm not on one of these things.
As far as I know, most airlines are seeing the 737-MAX 8 and its predecessor, the 737-800, as interchangeable (or they did until yesterday), so I doubt they will be able to say with certainty which aircraft type will operate a given flight...
Yeah, in my case it was a pretty straightforward situation with 1 airline not having the 8max at all (despite an article saying otherwise?) and my other flights being on 737-700's. I read a fair bit about this whole mess today and saw some posts saying there was a way to use SeatGuru to reliably distinguish between Max 8 / legacy 737-800, but I didn't need to dig that much myself and as you noted especially for flights far out, they can't guarantee equipment won't be swapped.
The MAX is pretty easy to identify visually. The engine nacelles have those chevrons like the 787 and the APU has a conical exhaust (look at the back of an older 737 and it's flat like a screwdriver turned sideways).
