Yes, there is a trend for "credit crunch lunches" and so on at the moment.
Will a mobile operator reduce their charges? Maybe.
It's a business decision and will be based around how much extra business they can get at what cost. I wouldn't be surprised to see T-mobile do something, but wouldn't expect e.g. 3 to do so simply because they appeal to different demographics.
Asda, tesco and fresh will be ones to watch, although personally I'd stick with one of the bigger operators unless your financial situation becomes really dire.