Yeah, I was reading about this today. Basically the CBA states that if a player in the final year of their contract is on the reserve/PUP list for the first six games of that season then their contract tolls to the next season. So he may be under team control for 2018, but it sounds like it's not definitive yet. Maybe some sort of hearing, or appeal?
While the Vikings didn't pick up Teddy's 5th-year option, they may have known that by keeping him on the PUP for the first six weeks that this would be the eventual outcome. If it comes to pass, they'll have a QB option for 2018 at a reasonable price, then can decided who else to bring in at QB for next year.
Not saying that Minnesota did anything backhanded or dishonest. Just protecting their interests under the rules if this is in fact the reason for keeping Bridgewater on the PUP as long as they did in 2017.