While it may be within the realm of possibility, so are a lot of things. What do you base your assertion on? Have there been any actual reports from trusted media members proposing this to be the case?
From what I've gathered up to this point, the Rams have reportedly checked in with Aaron Donald and both are comfortable with the timeline of having a deal eventually worked out, which some have speculated means that they're waiting for Khalil Mack to get his extension done first in order for the Rams to top that so that AD can be the highest paid defensive player in the NFL. I happen to be convinced of that, especially since the front office has also gone on record as saying that they've set aside current money in order to pay Donald.
Now that doesn't mean that the front office has set aside $20 million this season to pay Donald either, but rather that they've figured in a theoretical amount (say $6 million) to be added over the next several years as a spreading out of his proposed signing bonus.
Given that we still have about $25 million in salary cap space and aggressively tried to re-sign Sammy Watkins as well as offered Tyler Eifert around $8.5 million in free agency, I'd say that we should have enough money to pursue Ndamukong Suh since his price tag is anticipated to be around the same amount that Sheldon Richardson signed for recently.
Plus, the Rams have yet to address improving the run defense, which has been a stated priority for this off-season, especially with the departures of both Alec Ogletree and Robert Quinn. Signing Suh or Jonathan Hankins, for that matter, would fit the bill.