So I'm thinking of weaning at 6 weeks instead of 4 weeks for show pigs. Will sows cycle back at about 5 days after weaning if I add these 2 weeks??

No guarantee. If she has enough condition she could cycle on her own in those 2 weeks. Then she wouldn't cycle at 5 days

The biggest thing is how much she is eating and how she is looking. If she's starting to get skinny your chances of success are less. I don't think the issue is whether she will cycle. It's whether the breeding will take. She should cycle no matter what.

If you are targeting breeding at 19 days from now you could wean and use Matrix.