The Nepenthes do not go dormant, however depending on the species they may be fine with temps in the 50s in your greenhouse or just being kept in a windowsill in your actual house. Again, with no dormancy they need sun and keep them moist. These are from tropical regions.

The Sarracenia do need an actual dormancy. They are naturally growing primarily along the east coast of the US and Canada, and most can handle a similar winter to something in that range. Done correctly, you can keep most hybrids an species outside all year. Check out this blog of a grower who does that in zone 6 as well.

https://zone6b.wordpress.com/

Yes keep them moist, no not soaking wet and standing in water like you'd do in the summer. If your temps are in the 50's then they still need some sun, that's a little on the warm side but totally doable. In the 50's and no sun will just have them struggling and rotting. Read Barry Rice's FAQ, it says flytraps but care for Sarracenia will be the same. Then decide what way would best work for you to give them a proper dormancy.

http://www.sarracenia.com/faq/faq2360.html

Hopefully those 2 sites should help answer your questions!

Thx