Launched in 2007, Tumblr has been successfully growing in the shadow of other social media platforms; Twitter, LinkedIn and Facebook to name a few.
Tumblr makes it easy for you to share text, photos, quotes, links, music, and videos, from your browser, phone, desktop, email. In recent times, they even talked about video uploading. In essence it is the same platform as Twitter only with features that make it slightly more simple to use.
Is Tumblr the NEW Twitter? I very much doubt it. Twitter is still thriving and I don't see this changing for a good 18 months to 2 years yet. There is still a gap in the market for Tumblr but more a feature of adding value to your current social media strategy / business.