Overall, I think that these savings will be shared between consumers and businesses, but the FlyerTalk community that rakes it in on credit-card sign on bonuses are the folks that are going to get gored.
The CC profit model has shifted from risky debt that people might have trouble paying off to one based on volume, and a decrease in interchange fees is going to affect the profitability of Amex SPG or Chase Sapphire Preferred customers (folks that probably don't carry a balance but might have huge monthly spends). As that profitability is reduced, the sign up bonuses and awards are going to shrivel up disproportionately.
I'm going to snag as many bonuses as I can in the next 6-8 months; I feel this bizarre gravy train of travel perks for credit card sign ups is at risk.