I think you're ignoring the x-factor Novak. I think he's very close to getting back to his best. Once he does then it will impact both Fed and Nadal.
Novak is very strong at AO, so Fed won't be able to likely win more AOs with Novak back to his best. Similarly Djokovic has beaten Federer at Wimbledon, so even SW19 might not be a guarantee for Fed. For Nadal as his form declines YOY, it is hardly inconceivable that Djokovic could best him at RG. The only slam left is the UsOpen which is open - what with Zverev, Cillic, Delpo and perhaps some other young guns making noise over there.
Overall, I don't know how long Federer and Nadal can keep winning slams. Things change fast in tennis. We have a recency bias and believe that the current state of affairs will continue. But it probably won't. The most immediate dangers I see are Novak and Zverev. We all know what Novak can do, but even Sacha is rapidly maturing and might be a genuine slam contender as soon as Wimb/UsOpen this year. If I had to bet, I'd say both Fed and Nadal won't win too many slams going forward.
Lastly, no I don't think Nadal catches Federer in slam count. I think AO 2017 was the final nail in the coffin of that discussion. The gap's just too big now and will likely grow as Federer wins slams.