I'm mostly wondering what will interrupt them, 'cause frankly I don't see it actually happening. The series so far is too "low drama".
a) Asuka herself decides otherwise. Could be, if she gets another "I actually like mom" flash.
b) Jun comes to her rescue. I mean, he could be useful for once for something!?
c) Ayako randomly runs into them and thus inadvertently rescues her daughter. Obviously this fits with the romance-theme of getting rescued by your love interest.
d) Akira is coming back from a trip (again) and rescues her. That'd be a clear indication of the threesome route (no way ^^)
e) Rui somehow comes to her rescue. This might lead to their "reconciliation".
f) One of Miyuki's lovers/girlfriends/whatever interrupts them, thus screwing up her chances with Asuka.
g) Miyuki herself decides otherwise after she notices Asuka is into someone else (fat chance ^^)
h) Aliens.
Tough to decide honestly.