Target _blank is still good under html5 (Features)
There were several things they originally thought about deprecating and then reversed on, so I looked it up and target _blank is one of them. To quote the W3 website:
NOTE The target attribute on the a element was deprecated in a previous version of HTML, but is no longer deprecated, as it useful in Web applications, particularly in combination with the iframe element.
Here's the page a -- hyperlink