If you are really concerned you can invest in a flex fare which allows you to recoup your money if you have to cancel up to a day ahead - NS International has those. Also Eurostar has flex, but they have different classes of flex.
A strike makes your Eurocity or Eurocity Direct ticket flexible. You may take any Eurocity or Eurocity Direct train on the same day, or even a day earlier or later. You do not need to change your ticket to do so.
Please note: if you have a Saver ticket, this may still result in additional costs.
If you have a Eurostar ticket, you can request a refund if your train is canceled due to a railway strike in Belgium or the Netherlands.
By the way, there is NO chance of another railroad strike in Belgium this month, since the unions won't meet until November 9 to assess the situation.