It's going to be interesting to see what happens, but I wouldn't expect to see anything significant on any specific date.
IMO the rule is a step forward and should help, but whether it's enough, or will work remains to be seen.
Last summer and fall I know for fact that at least some of the more notorious Canadian, namely Vancouver based firms, started not accepting short sales without borrows on OTC stocks....so really as far as the average "smaller time" shorter is concerned that was using those firms, the rule has been in effect for many months.