I can see a retractment from Blizzard, but it would really depend on just how many people are cheating/hacking/modding the game to the extent that it warrants a ban. So far, this hasn't really made any significant headlines. If 10% of active SC2 players cheated, then yes, it's a big deal. If it's just 1-2%, Blizzard could very much say "well **** you, we made the game and this is how it's going to be played".
IW took a similar stance with MW2 PC by not enabling a dev console. Did that stop people buying the game? Nope. SC2 is arguably PC's most anticipated game since the first one, that alone will generate some serious dosh. If a handful of players get banned, they won't be losing any sleep over it.
If a lawsuit gets introduced (which looks like a slim possibility), then the **** will hit the fan. I don't agree with Blizzard's decision on this one, but the majority of SC2 players (to my knowledge) are legitimate players, sans cheats.
If I start using the trainer and they ban me, I just might be the one who sues them. One way or another, Blizzard has to do something.