Action:

50s isn't cold enough to keep the plants dormant or give them chilling. The strawberries will be growing and the blueberries won't get enough chilling. I'd urge you to do what's worked in the past.

An area in the low 30s would be best. But even that won't be as good as buried outdoors. They need water only if they have leaves.

actionclaw,

You mentioned that you "mulched" with leaves. I'm not sure if that means you put leaves on top or if you bury the pots in leaves. I also live in Northern Ohio (south of you). I gather my potted plants into a cluster and bury the pots in leaves (not the plants themselves). My plants include potted blueberry bushes and cherry tress, but not potted strawberries. I've been doing this since 2010. We haven't had an extreme winter during that time, but so far winter hasn't killed anything. In my neighborhood, leaves are still plentiful. And our neighbors are happy to dump their leaves in my pile. However, I have a pile of leaves to get rid of in the spring.

You don't have to gather the pots. But the overall quantity of required leaves will be higher if you don't.

disclaimer: on another thread, someone lost plants to rodents when they used a similar method.

OK, so the basement idea is out.

Normally what I do is plant pot and all in the ground (at about the same level) then mulch with leaves or (finished or unfinished) compost. So far, it's always been successful.

I suppose my current main concern has been that the (soil, roots, etc in the) pots may freeze solid. I don't know what the frost line is for this area (northern Ohio) but as it's, in some cases, 6" or so pots were talking about, above or below, they're probably going to be freezing. If mulching etc is handled the same, will in-ground versus below ground, in this case, make a significant difference?