I think you're right in both important respects - that inequality is a huge problem and rising (I am convinced by Piketty's arguments). The 'end of history' may not be a liberal capitalist one - but an illiberal capitalist one, in which no states or institutions ever become powerful enough to challenge capital oligarchy. This is wild speculation, however!
The prospect of secular stagnation is a real blow to the idea of permanent exponential growth - if you do look at what has happened over the last few hundred years, the expansion of energy resources and the violent conquest of frontiers by industrial-capitalist states has driven a lot of this explosive growth. When we do reach a point of saturation of energy availability, it may be the case that however advanced new technologies become, they do not nevertheless drive the kind of economic rates of change that the last two centuries have seen.
I do nevertheless think it will be plausible that we will attain enough control of energy and mineral resources and attendant technologies that space colonization and posthumanism for a great many people are realistic possibilities, and it is very important that we safeguard these and make sure they happen in the way we want them to!
I do enjoy your blog and I thank you for your kind comments.
Cheers,
Ben