Nothing absolutely nothing in life is guaranteed except death and taxes. One should think only in terms of possibilities and probabilities. It is probable that a pension will be honoured as expected; it is probable to a factor 0.5, 0.75 or 0.99999 that it will be paid - take your pick. However it is possible that it may not be paid at all - Robert Maxwell.
We have always assumed that anything backed by a (reliable) state would be gold-plated and as guaranteed as it is possible to be. That may no longer be the case in the current crisis and new economic order which may arise from it. What if a supposedly mature Western state goes bankrupt? Iceland, anyone? Argentina? What price that state's pension liabilities then?