I'm pretty sure Duran and Ronayne O'Mahony are confirmed at Hitech, although the team is unlikely to admit it.
Hitech, Fortec and Double R are all running 3 car teams with Mercedes engines.
Autosport confirms that Bakkerud and Jelley have signed, as you say, and I would be very surprised if Senna were not to stay with Double R.
Karl Reindler is likely to stay with ADR, who may also run Jonathan Kennard in the Championship Class.
The question marks are over Mike Conway and Charlie Kimball, one of whom may switch to the Euroseries. It would be a mistake, imo, but drivers are not always rational.