I think we will see working fusion before we see geothermal power of that sort. But we will have much better batteries and other improved energy storage as well as cheaper solar/wind/wave power, better, longer grid interconnectors and probably modular nuclear reactors before we see working fusion. Whilst the successes of the most achievable technologies won't prevent ongoing work on less achievable ones it may be the problems they are intended to solve will get solved without them.
All we have to do is to build these nanobots that will harvest minerals from NEOs and will self-construct this solar array.
ALL? Seriously? Using non-existent "Nanobots" is equivalent to relying on magic. There is nothing inevitable about such technology.
Any factory that makes solar panels will draw on multiple specialist suppliers as well as connect to pre-existing essential services, many of which will not be viable or exist at all except that there were and are other uses and users. Between imagining nanobots that can do it all, from the very limited minerals available in asteroids - and I seriously doubt it even can be done that way - and designing and producing them is a vast amount of R&D that is unlikely to happen if it relies on such speculative projects to provide sufficient motivation. Some Earth based reasons for developing such technologies may allow other uses to develop as spin offs but asteroid mining, whilst conceptually simple, will be very complex and difficult and it is unlikely to be attempted with nanobots, even if they existed.
Space solar has been an idea around for a long time without any significant progress. I've always wondered why, if it is feasible to beam power down from space, can't we leave the solar farms on Earth and beam power up in one place and back down somewhere else? Well - poor energy conversion efficiencies is probably one reason why it is not given consideration. Like many of the "just do X" solutions, it turns out being a lot more difficult and potentially expensive than the optimists say.
In my experience the proponents of such clean energy solutions are usually grand space optimists for whom the massive expansion of space capabilities is the principle motivation - very often with the intention of leaving Earth and it's problems behind rather than fix them; it will not go down well for our very serious Earthly concerns to be misused to advance entirely different objectives.
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However, seeing as how I'll be long gone before such schemes are operational, have at it... 
