There's no such thing as a commodity - especially in a business where people deliver to people. Are you a commodity? Are you Lidl's own brand coffee or Starbucks? Oh, coffee is a commodity isn't it?
Consultancies which are little better than temping agencies may struggle - but there is even a premium for having temp staff rather than employing someone during a recession.
No, you won't see lower charge rates. You might get paid less yourself, and you and some of your colleagues will be sacked. But rates will remain high.
Of course, consultancies stuck in an hourly rate business model may struggle - they fail to understand, communicate, deliver or price for value-add. That's why the rates will stay high (although in some cases lower than they should be) because of this blindness.