While Trump did not officially recognize Taiwan, or even physically receive a foreign diplomat from the the government of Taiwan, the phone call still breaks decades of tradition in relation to our country's support of the "One-China" Policy.
On a side-note, but possibly of political interest, it has been reported that Trump wants to build luxury hotels and resorts in Taiwan. http://shanghaiist.com/2016/11/18/trump_taiwan_expand.php.
Here are articles from the WSJ and the Hill on the subject that I think also give a good picture of the situation:
Maybe this means nothing for the future of our foreign relations with China and is just a possible signal of Trump's political tactlessness, or maybe this is a reflection of Trump's anti-China rhetoric we saw on the campaign (in relation to outsourcing jobs and such).