Austin's potential dead money in 2018 is not significant ... and let me explain.
Austin's cap hit in 2018 if he's still on the team is $8M. If the Rams cut him there's $5M in dead money to account for, but there's also an additional $3M in cap space that the Rams can spend.
Suppose Austin fails miserably in 2017, the Rams cut him in the offseason, and then the Rams sign a FA who has a $3M cap hit in 2018. The net effect of cutting Austin and signing this hypothetical FA is $0 in the Rams 2018 cap: $8M for Austin if he stays vs. $3M for the FA plus the $5M dead money for cutting Austin.
AlbaNY_Ram