Peggy, I seriously doubt there is any such regulation; if there were, how could ships like the Caribbean Princess - 3150 passengers - sail at all?
With respect to dining space, I would expect that the ship's designers would provide extra space in Compass Rose and Veranda in a larger ship, particularly if suites were added, but it's an excellent point to raise with Regent's management during the cruise starting March 14th.
I must say though, that in all our years sailing with RSSC - both brands - we've only had to wait for a table twice, and once was because four of us went to, I think, Latitudes, and didn't want to risk the menu (there were two who were alergic to fish). The CR matre'd escorted us to the near-by bar and told the bartender to put our drinks on his tab, meaning as many as we needed according to that bartender, urging haste, but we only had one apice before we were seated. Obviously, this was before 'all-inclusive' came into play.