Sort of, thus the term "Sincaraz." But I dislike everything being compared back to Fedal or the Big Three. Tennis history is full of rivalries and/or pairs or small groups of greats separating themselves from the pack. And each rivalry has its own qualities.
So yes, in that there's a big gap between Sinner/Alcaraz and the field, just as there was between Federer/Nadal in 2005-10. But no, in that I don't see the dynamic playing out in the same way. But we shall see, just as we'll see if there's a third great going to emerge alongside them like Novak did, and whether the gap will be as extreme as it was with the Big 3/4.
But tennis has always been dominated by a small group of players. I mean, consider that over 80% of all Grand Slams in the Open Era have been won by just two dozen players (3+ Slam winners), and two-thirds have been won by just 14 players (5+ Slam winners). Different eras vary from the mean, but in general, two out of three Slams have been won by players we consider to be "all-time greats."
Regardless of how good they become, I think it is safe to predict that both Alcaraz and Sinner will be considered all-time greats - they're pretty much there already, but just need a bit more padding to their numbers. So chances are, for the next few years at least, they'll be winning the majority of Slams between the two of them. But will they win 11 in a row like Fedal did from 2005 RG to 2007 USO, before Novak won the 2008 AO? Who knows.