If I log out of one device but currently logged into another device will the photostream still be on the other device?

Hello Brian_B24,

Thanks for using Apple Support Communities.

If you disable Photo Stream or log out of iCloud on a device, the photos displayed in Photo Stream on that device will be deleted. However the photos will remain in Photo Stream for the 30 day storage limit, thus keeping them on your other devices.

My Photo Stream FAQ - Apple Support

Take care,

Alex H.