Cohabitation is inevitable in my opinion. Both offer similar services in different ways. People will always depend on banks while they will also embrace the advantages that cryptocurrencies offer.
Well, they don't technically offer the same services. Banks are a byproduct of a capitalistic world, and have essentially created a business to cater for the masses. While, Bitcoin is applying to those that want the freedom to manage their own money, without any limitations. Banks, aren't offering any freedom at all. In fact, if you look at their policies I can almost guarantee that they limit you in some way or another.
The only real benefit to banks, and in essence reversible transactions is; fraud protection. That's really the only benefit to them. Of course, cohabitation is almost a given, and in fact probably beneficial. To be honest, some people prefer to have others holding their valuables, since they don't trust that they can do it themselves. So, having a bank manage your finances isn't always bad, depending on your specific needs. However, I think its quite clear that I'm not a massive fan of banks, and I've definitely had my fair share of issues with them in past regarding sending transactions.