I have a few different ideas regarding this challenge. One of the first things I thought about was the fact that most of the research dealt with how digital experiences can be improved to increase usage by older customers. While some in their 50s and 60s have adapted well to the digital world, there's a significant portion of that population that will never be comfortable navigating digital products.
While there is a trend for large banks to focus less on the growth of physical banking locations, it's important to note that smaller banks are still expanding heavily as far as physical banking locations are concerned (source below). Also, there will continue to be brick and mortar banks for the foreseeable future. As Gaurav Lal mentioned in his post, it's important to understand that older customers still prefer face-to-face interactions, especially when dealing with personal finance matters (maybe digital video solutions could be effective). While digital solutions are the "sexiest" opportunity for innovation, the customer experience in physical banking still has plenty room for improvement. These changes could attract more young and old clients alike. Check out how Capital One is introducing cafe-style banking locations in the sources below.
Growth of physical banking locations: http://www.marketingcharts.com/traditional/banks-more-likely-to-increase-than-decrease-physical-branches-with-one-exception-67755/
Improving the Physical Banking Experience: http://www.wsj.com/articles/is-this-a-coffee-shop-or-a-bank-1436225586
Another important point is that not all financial services are being included in the discussion. Longer lifespans and an older population pose huge implications for private financial advisors and wealth managers. Perhaps improving the experience for older clients has more to do with developing new complex software solutions that can better model ideal portfolio allocations to ensure that clients retirement & savings needs are being met adequately.
Financial Advisor Discussing Implications to Industry: http://www.edelmanfinancial.com/education-center/articles/q/qa-how-does-a-longer-life-expectancy-affect-your-investments
With that being said, digital offerings are definitely not being designed to cater to older populations. There are 50+ year-old technologically savvy users. There are simple design tweaks that can be implemented to better cater to this demographic. Maybe all websites or apps should have an "elderly user" mode (hopefully with a nicer name).
Design for Older Users: https://www.smashingmagazine.com/2015/02/designing-digital-technology-for-the-elderly/
I know this post is on the lengthy side, but please let me know if you have any comments or suggestions!