Dude was 45 when he debuted as Bond and made
seven movies
Probably the biggest black mark against his era is that by around For Your Eyes Only he's starting to look knackered and rough around the edges, and in his last two films he just looks ridiculous. Also, the franchise needs to make a choice when the actors are older anyway: if they're going to do that, they need to be comfortable casting older women as the primary love interest. Obviously they did this a bit with Belluci in Spectre, but they cut half her scenes and of course she was a secondary interest. There's those scenes in For Your Eyes Only where Moore's Bond is with an 18-20 year old and it's just
nuts.
Anyway, the main point is this, I think - I don't think they'd ever let a Bond actor age to Moore levels again. Even then they knew it was wrong - Moore was leaving, then the whole McClory produced Never Say Never Again Connery film came about and the producers got nervous and decided recasting would be too risky while the franchise had a direct off-brand rival, so we got Octopussy and View to a Kill. Moore was 57/58 during AVTAK filming which is just crazy. They're not gonna get to that again, and they're going to want to try to cast somebody who can be in the role safely for around a decade... so Mid 40s is the absolute maximum they'd go to, I think.
Hardy's a great candidate, I think, because we know Nolan wants to do it, we know Nolan would cast him, and presumably when Craig goes he'll be 42 or 43, so he's basically right in the sweet spot. Cavill is also in the exact sweet spot and will be for about the next ten years, though I wonder with him - he's done so many Bond-like roles (MI, UNCLE, etc) I wonder if they would now view him less favorably?
I never thought Idris stood a chance of getting cast because he is too old now, I think (he could play a very convincing Bond now, but the producers will want to think five to ten years ahead), but I think the producers joking and teasing and saying he'd be a great Bond is their way of signalling to the public and fans that the next time they cast they're going to be open on race. There are other Black British actors who could do an excellent job, and there are even people in their twenties (even Boyega comes to mind, tbh) who in another ten to fifteen years when they're the 'right age' for Bond could really do it justice.
A really,
really important note about Cavill is he was second for Casino Royale. Director Martin Campbell actually even preferred him over Craig, but given his age the producers declared he was too young and so they went with Craig. During Craig's era Cavill has matured right into the look/feel of Bond, and at 35 he's now exactly in the age bracket the producers like and will be, like I said above, for about the next ten years. We also know he wants to do it - he said in an interview he'd love to replace Craig just last month, even.
