I agree it buys them time. He wasn't as good in 2016 as 2015 of course. And however you want to read his numbers he's a solid starting CB and it's very true that if they let him go then
at best their secondary treads water in 2017. It won't improve. I also believe the idea of seeing if he really does fit Phillips system. Plus for all we know a longer term deal still could happen. I also think the Rams' poor pass rush- and it was poor most of the year- hurt him as it would any CB.
But a CB group of Johnson, a draft pick at #37, Joyner, Gaines, and then Hill/Johnson would be just fine with me. Personally I thought Hill and Johnson showed potential. They ended up being thrown to the wolves a bit too soon but as 4th or 5th CBs I think they could continue to develop. I watched Jordan play when he got thrown in vs. NE and while Brady went right after him and he gave up some catches he didn't get torched or give up YAC and played hard.
Of course in 2018 then you have Johnson, Joyner and Gaines all UFAs. Let's say Johnson and the Rams finally do part ways. Well then take the CB you drafted at #37, $16M+ in cap space, and prioritize a CB again next year. Plus get a 3rd or 4th round comp. pick in 2019 for Johnson.