Frankly, I see it as yet another example of sensationalist media reporting, first and foremost... "double mutant" sounds scary for sure, but it's not particularly unusual, and there are probably hundreds of similar other variants circulating unnoticed already. This particular variant has been sequenced in India last year already, has been found in numerous countries, might be more contagious, but so far, there is no evidence of it being able to successfully bypass T-cell immunity or evade antibodies, nor is there anything to suggest that it is more deadly or causes more severe disease. So in short, basically the answer is "there's not enough data", as usual.