That's not a new kind of search engine, it is a frontend for bing that can be used without the shame of having to say you use bing.
As far as I know, nobody is building a new kind of search engines, although I'd guess that a new kind of search engine won't really look like a search engine at first.
I thought it was common knowledge that DDG uses Bing and a few other sources, except Google. The difference is that they don't track the users in any way and they don't put ads on the page. The fact that it uses Bing is why relevancy is not very good on DDG, though.
I think DDG is best considered a search broker, it federates the queries out to other engines, like bing, or others under query syntax control, and I believe they are also crawling some or their own content, although that's mostly beyond any individuals capability at this point because the internet has become quite large. The broker also merges federation sources, however it isn't a search engine in the traditional sense because the indexes (posting lists) are in google, bing, lucene etc.
As far as I know, nobody is building a new kind of search engines, although I'd guess that a new kind of search engine won't really look like a search engine at first.