With the way the Rams are operating these last couple of years they seem to be banking on the salary cap ballooning with the new cba
No they are doing proper cap management. It's clear Whit and Talib won't be back and they alone account for $24.6M against the cap. Brockers is on the bubble as his production doesn't balance with his $10.7M cap hit. Troy Hill and Nickell account for another $8M and IMO both are bubble sitters, especially Nickell. They already cleared $5.8M off the books with Peters. That's $48M right there.
Right now the Rams cap hit is $184.4M leaving them about $5M for the rest of the season, which would seem adequate. In 2020 things get uncertain due to the expiring CBA. But projections are for the Cap to rise to about $200M which means about a $11M increase. Factor what I've posted above and you can see they should have between $60-$70M in cap space next year. The CBA complicates signing extensions which accounts for why some teams have been waiting on extending people.
Regardless I see no need to worry about having the cap to sign their key players to nice extensions.