Well, assuming the normal pattern continues, no, it won't be replaced. Unlike these other black-and-white shows, the pattern hasn't been for What's My Line? to come-and-go. It's stuck around pretty consistently -- hence why see various references in the guide to airings within the "regular rotation." Of course, we did have a pretty large stretch there where GSN was only airing the Black and White Overnight once-a-week and the rest of the overnight slots were filled by repeats of The Amazing Race. That's over now, though, and hopefully isn't coming back.
In any case, what you're talking about is still a ways off. Given how many of the early shows were lost, the truth is that we actually are in what's considered the early portion of the rotation. Assuming once a day airings continue, it's going to be close to two years before it returns to the very top of the order.