When the temperatures get to 50df in the bin, it is like putting food in your refridgerator to keep it from spoiling. All the microorganisms and bacteria (and worms) just go to sleep. They do not die, and as soon as temps go to 60 and above, everything wakes up and starts really feeding more and reproducing.
So..yes your worms would become much more active by warming them up.

50 is not the end of worm activity, although what you see may change as they'll be more inclined to avoid the surface - nor is 60 the beginning of activity - worms do slow down as temps decrease, but 50-80 is an acceptable range, much below or above that and worms descend and cluster, and while the particular microbial varieties may vary, there are bacteria that are most active at low temps, just as there are different ones active at higher temps - psycrophiles [32-60°C], mesophiles [70-100°F and thermophiles [above 115°F], unlikely to be found in a worm bin

what's relevent is soil temp, which varies less, and can be well above, average air temp

Bill