There are talks that Google's famous spam blocking service reCAPTCHA will soon be a premium service. Rumours are that the free version will cease to exist.
But looks like it is rumour after all. Premium is only applicable if you go over 10 lakh queries per month or 1,000 API calls per second. So if your project is small or mid range one, there is little reason to worry according to the news circulating right now.