I agree on Pegg (and with Will on Bloom) and I don’t think we’ll see the character in his own movie anyway.
But I do think there is a Captain Britain movie that could be made that would find a big audience; amping up the Britishness with as much Arthurian-lore and other stuff as possible. It’s just that Marvel just don’t need to make it. They have plenty of other projects on the slate.
Disney might look at it as a TV series though. The tax breaks make the UK a good location choice and shooting shows with regional appeal is a good thing for a global company to do.