With solar energy prices down over 60% in the last few years and the cost only looking to drop further. Can solar energy be a realistic long term solution globally?

Well, it is looking that way. Especially in certain parts of the world which benefit from an agreeable climate. 

Once deemed as an expensive alternative energy solution, the amount of innovation and cost cutting within the supply chain has turned a once hard sell into a viable long-term and sustainable solution. 

Many will argue that intermittent electricity solutions such a solar and wind may not be suitable for many locations but with today's sustainable agenda and the focus on carbon emissions globally. I can only see solar becoming more commonplace. whether however, this is via large solar farms on an industrial scale or from people taking a more individual solution for their needs such as Tesla's home solutions remains to be seen.