I say stick with your Premier Pass (should be ThankYou Premier now) card and maybe a Delta Skymiles card if you fly Delta a lot and want free bags and access to the lounge. The Premier gets you no fx fees plus a discount on purchasing airfare thru Spirit Incentives. You also can effectively get 2% back or more on that card when you match spend points with flight points.

The BA Visa I would get rid of when the annual fee comes due. Many changes will be coming to that program and the fuel surcharges on BA metal are just ridiculous. JetBlue card is not all that great imho.