To all: Thanks!
Yes, I see on FlightAware that the first flight today goes out of Gate 43 in the Main Terminal; if this continues next week, the only option is what aa.com says: the lounge for AA 26 being the Asiana one in the Concourse, also unreachable from the Main Terminal (actually, as you know, "reachable" but no return is possible). I wonder if the other Asiana lounge (the one in the terminal) would also be available in that case? AA can't answer this; I asked.