There will always be some liberty, at the end, otherwise there would be little to plunder.
Politicians will only move further toward socialism for ignorance, ideological blindness and political instability. The last reason is not a concern because the masses still firmly believe in democracy, despite the total lack of good reasons to. The others are self-correcting in the long run, except when the political process forces short-run strategies to assure reelection, turning democracies into "apres moi le deluge" banana republics.
Politicians will prefer to destroy the society they exploit only when they are not sure of their power, when they are prisoner of ideological commitments devoid of reality (or need commitment to stupid ideas to remain in power), or when the political process incentivizes short-termism.
Politicians will only move toward liberty if constrained by laws, customs, ideologies, constitutions, fragmentation among autonomous power groups. It cannot be denied that all these factors have weakened considerably in the last century and a half, so they cannot be relied upon very much. Surely not at all in Europe, at least. Law is the will of the powerful, power groups are political beggars, constitutions are a populistic menu of positive rights administered by the ruling elite, markets are ruled by those who can obtain privileges and economic autonomy is an exception because everybody depends on the state.
The reason why liberty is always an unlikely outcome (beyond the efficient level from the rulers’ point of view) is that liberty is a public good, while power is a public evil (and thus overproduced in all societal settings). Those who fight for liberty fight for other people’s liberty, and they have nothing to gain. Those who fight for power fight for their power, and they will be able to exploit the rest of society.
However, markets are so comparatively more efficient than slavery that even without institutional contraints against power there will be a lot of economic freedom.
Here’s a libertarian conundrum: in order to have more liberty, blind faith in democracy – the latest instrument for the expansion of poltical power – must diminish; but if political instability ensues, it is far more likely that liberty will suffer a further drawback.
Serfdom is a stable social equilibrium. Liberty isn’t.