Aryna is 27 so she might be entering her last few seasons of her peak. Not many women have been able to win GS-titles in their 30's. If she should complete the Career GS, it's not unfair to think she'd have to do it in 2026 or 2027 - maybe 2028. So probably 2-3 more shots at WC and RG. And you have to assume that players like Andreeva, Gauff, Mboko etc. keep improving.
Iga for sure will get it. Just a matter of time.
Who gets it first? Probably Iga, since I'm not entirely sure Aryna will complete it. She's already wasted way too many golden chances, and she's not exactly Serena, who was a reliable GS contender even in her mid 30's.