Recently, Google has come up with a new update of extending the search results snippets from 160 characters to a maximum of 320 characters. Also, Google has made it clear that the fundamentals of writing a meta description will continue to be the same. However, there isn't much clarity about the concept as of yet. There isn't much information if Google is going to display all of the 320 characters or if Google is going to show the meta description or content from your page. If there's one thing for sure about Google's way of handling the snippets, it's the fact that it's solely based on the search queries and the relevance of content on a certain web page.
According to a Google spokesperson, it'll be too early to give it a try to expand the meta description and there's absolutely no need to do it as long as one is happy with the current ones. He further added saying that nowadays they add slightly longer snippets to display more of the meta description. However, if you aren't happy or if you want to experiment with it, you can always go ahead. There's certainly a lot of talks going on about this sudden update if existing metas should be updated by the SEO or expanded by Google instead. Some believe it can improve the click-through rates. However, from the technical perspective, meta descriptions don't really contribute to the ranking of a site in any way, be it long or short. It can at the most determine the way your site should be visible in the search results.