I just called the Lufthansa Service Center regarding our abovementioned flight on Friday. Of course they "didn't know if the strike would go into effect" at this time, but during Tuesday or Wednesday, all affected passengers would be contacted regarding rebooking or refund, if the strike goes into effect. Hopefully they will find a solution by then.
Could we have a chance of being rebooked to eg. Brussels Airlines BLL-BRU-VIE (of course depending on availability), or would that probably not be an option?