Yes, TRIIICK, it's best not to bet your life on what you think that other folks on the road might do.
One of my greatest concerns when riding is that it seems that at least half of all motorists fail to signal when turning at all or they apply their signals very late, leaving me to guess what their intentions are. It is not healthy to guess what they are thinking about doing in their multi-ton vehicles, so I either wait until they clear an intersection or complete their manuever(s) or I am conservatively prudent to a fault.
A good habit that I picked up some years ago is watching other drivers' eyes in their mirrors and/or monitoring their head movements. Often that helps me to figure out what they are up to before they actually do whatever they might be contemplating.