I believe that eventually the industry will settle on one standard format, but that day is a ways off. Too many people are making money off the current situation for it to change anytime soon.
Meanwhile, as we wait for the situation to sort itself out, there's something you can do for your own collection in the meantime. Using Calibre with the right plugins, it's trivial to strip the DRM and convert to whatever format you like. My general practice right now is to buy epubs, de-DRM them and then do a conversion to mobi, storing both the epub and mobi versions. It works the other way too, if you like to buy from Amazon.
That way you'll have books that will work on just about anything, and you won't be locked into any one particular vendor.