Word is it won't be as low as expected. It certainly won't be 50M. It probably won't even be 53M. 54M+ I think is the understood numbers the league is dealing with.
It's a moot point however as a max contract is based on the cap number. The lower the cap the lower a max contract - so in theory it doesn't mess up a team's desire to sign a max FA just because the number lowered.
If you can afford a max FA today you can afford one tomorrow regardless of how far the cap drops. Max contracts are a fixed percentage of the cap. So the cap drops, the max contract numbers drop, and you'll still be able to afford one.