As a user of both Flickr and SmugMug (and, full disclosure, a former SmugMug employee), I think the two sites have different but complementary strengths. I don't think the goal should be (or is) to migrate Flickr users to SmugMug. I think these are two services that can coexist and work well together.
Flickr is more of a casual social place to share your photos and see photos by other people. It's the closest thing we had to Instagram before there was an Instragram, and I think casual social photosharing is still what Flickr is best at.
Except for the photos themselves, everyone's Flickr photostreams, albums, etc. look the same. They all share a consistent sitewide design that looks good and works well, but that you can't customize. This is where SmugMug comes in.
SmugMug is completely customizable. You have full control over what pages are on your SmugMug site, what functionality those pages have, and how they look. You can use pre-built templates to get functionality similar to Flickr, but you can also fully customize SmugMug to be the homepage for your photography business, complete with a portfolio, a shopping cart where people can buy prints and digital downloads, password-protected pages for your clients to review photo shoots, etc.
In other words, Flickr is a great place for casual social photosharing, and SmugMug is a great place for photographers to really showcase their best work, or even to run their photography business. Two great tastes that taste great together. 🙂