If I were the NFL, I would NOT want to add any more teams any time soon.
Not only is there the talent dilution argument, but 32 teams is just a perfect number. Each team plays its division rivals twice, one intra-conference division all once, one inter-conference division all once, and the two teams in the intra-conference divisions that you're not already playing that finished in the same place as you once each. No fudging. No accusations of bias (at least not in the teams themselves. The fact that we're playing in Seattle in week 17 again is complete Brian Schottenheimer.)
Once you add teams, you lose that scheduling perfection.
Someone's eventually going to move there. It likely won't be the Rams unless St. Louis and Missouri screw up big time, but there's no need to add teams at this point.