Blogger has not seen any major update since a very long time. We have seen Google kill their popular services such as Google Reader, Adsense for feeds, and the possible demise of FeedBurner. Future of Blogger depends on Google, and they have the right to shut it down whenever they want.
WordPress is an Open Source software which means its future is not dependent on one company or individual (Check out the history of WordPress). It is developed by a community of developers and users. Being world’s most popular content management system, thousands of businesses around the globe depend on it. The future of WordPress is bright and reassuring.