released a couple of days ago -- and, of course, no news yet from CC when / if these will reach BB, but Bootstrap 4.1 is out -- It includes some nice improvements like: drop shadow utilities, carousel crossfade, and flex-fill/shrink/grow utility classes. You can read more of what has changed in their post
https://blog.getbootstrap.com/2018/04/09/bootstrap-4-1/?utm_source=Bootstrap+Creative&utm_campaign=884fb9513c-EMAIL_CAMPAIGN_2018_04_10&utm_medium=email&utm_term=0_270d4001c4-884fb9513c-1240842457&mc_cid=884fb9513c&mc_eid=67b6aeb845

I've seen it, and I have also sent off a question about it to CC. We'll see what they reply...

Thanks for the link Russell, I was unaware of the Bootstrap 4 update. As for Bootstrap 4 I think like Inger said its only a short time away. CSS Grid is updated and using Bootstrap 4 in Bootstrap mode. There was also a recent addon to being able to use the actual Bootstrap layout classes like col-md-6 col-lg-4 on an element to create your spans on a container. They have come a long way from RLM to RSD 1.5 to RSD 2.5 and now adding Grid Builder to the mix. Really hope to see more exciting things from this company !