The real time shipping feature within the shopping cart section is not a native feature of Shopify, however we can definitely put this feedback through on your behalf to our developers to consider for the future.
In the mean time, we can suggest a couple of apps that will provide you with the same output -
Take a look at these apps and try them out on your store so you can see if they are a right fit for your website.
What are the current shipping strategies for your business? Your shipping strategy plays an important part of your stores success. The right shipping strategy for your business will depend on a number of factors including audience, budget, margins, and products. We have a great resource here on planning a great shipping strategy!
I'm glad I could help! Feel free to reach out to our Shopify Community any time otherwise visit our Shopify Help Centre.
I wish you all the best with your store!