"Will new MST3K be exclusive to the Gizmoplex?"
Taken from Backer Update #15:
Yes, but not forever!
We're still working out the exact timing for this, but our current guess is that new episodes will be available exclusively through the Gizmoplex for a period of time – probably somewhere between 3 and 6 months. During that period, members will be able to stream them on-demand, and all visitors will be able to rent or buy them from the Video Counter.
After that initial window ends, the new episodes will eventually be added into the streaming lineup running on ad-supported platforms like YouTube, Twitch and Shout TV, and will be available for purchase from other video retailers and sites. As of now, Shout Factory is also planning to release a retail version of Season 13 on DVD and Blu-Ray!