No doubt they will like JJ, and we fans will, too. But the question at the end of the season will be: if Rapp, Burgess, Fuller, Scott, and/or Gervase can handle the safety positions would the Rams be better off with JJ or with $14M a year over the next 4 years? If the answer is JJ then of course they will sign him.
About the salary cap, though: if the NFL plays this season without fans then league revenues will go down and as a result next year's cap will go down. If my math is correct, from $200M a team down to $185M a team.
AlbaNY_Ram