Without wishing to state the obvious, why not look at a few routes for next week and see what is available?!

Don't forget that visa issues make some places difficult for short notice flights, eg Russia, India, China.

You tend to need a back-up plan though. I have some Cape Town seats booked for January, but I had to go fly to Jo'burg on a 2-4-1 and then use separate miles for a Comair connection. This is both slow and expensive in terms of miles. I am hoping to get direct Cape Town flights in the few days before departure (and thus cancel the Comair tickets) but if I can't then I will live with what I have.