There is also another 'factor' in the mobile banking App debacle that not many are talking about. BECU already has stated that all of their banking Apps will merge into a new 'mobile first' web interface that will give all users an amazing Mobile Banking Experience via their online mobile web site. They are choosing not to make another app because of the amount of money that is required to keep up with OS changes, security features and other issues. If everyone is dumping their Apps in favor of a more secure HTML5 based solution that is accessible through browsers, I don't see a problem with the Windows Phone Apps dropping away. If they are dropping support completely, then they will stop getting my money.
Currently BECU has my cash, and they have been very upfront about supporting WP and transparent about why they haven't yet. They have so many resources available for mobile users and 97% of the market uses iOS and Android - it's a simple numbers game. The universal app process may also bring some additional financial institutions along the way. We will have to wait and see if this is a sign of bad times ahead or if there will be an anti-Android campaign that is strong enough to break the mold and switch the numbers over to where WP would be profitable enough for many companies to add to their App selections.
All I can say is I'm glad I still have my HTC M7 developer edition... I might need it going forward if this exodus continues.