Is Apple Numbers replacing Excel?

Different products from different companies. Excel is not going anywhere as Apple ha son control over it.

Numbers is an Apple product. It's not imposed, it's available for free with Macs.

Excel is a Microsoft product and you need a paid subscription or one time purchase to use it.

If you want to continue to use Excel you are free to do so.

Numbers is a free app included with the purchase of an Apple device. It would be your choice as to whether you use it or a competing software.