Cheating through item drop mining with multiple accounts can't be done without paying for some in-game store item that makes the account a premium one, since free accounts can only be on the recieving end of a trade and have item restrictions (eg no hats).

If you mean the much more serious VAC-evasion by creating new accounts, they mentioned they would be cracking down on those, but no so sure about the specifics.

It's less of an issue than you'd think. People become incredibly vested in their accounts. Hundreds of hours of playtime earning items and real money to buy others. Not many players will risk their time and money investments by trying to cheat.

Aimbot is still an issue as you can make throw away accounts. If a game supports the concept of "high player level" servers it's less problematic.

I think the question becomes "Will people really want to make a new Steam account every time they want to cheat?"