I cited Doug Wilson’s blog (cleverly named Blog & Mablog) in my earlier post on Emeth, as he wrote in some detail on that subject earlier this year. Last year, he wrote on the subject of Susan’s absence from the ending of The Last Battle. Spoiler: he concludes that she’ll get there eventually.
Lewis himself, of course, allowed for the same outcome, though I’m not aware of his ever saying specifically that she would arrive in Aslan’s country–only that she could. But Wilson makes a pretty strong case that she would–“once a queen in Narnia, always a queen in Narnia.”