Somewhat, you can do that with CBSubs Promotions partially. On the advanced tab you'll need to set "Single payment (and for autorecurring payments subscriptions: First payment amount):" to "No" and ensure "For Autorecurring payments subscriptions only: Second and following auto-recurring payments amounts:" is set to "Yes". You'd basically discount the purchase by 3 days worth of payments. This won't give them 3 days then charge them, but they're having the price reduced by 3 days so more or less are getting their 3 free days. Below is example configuration.

Basic
Promotion Type: Applies to all purchases
The promotion is: A fixed amount
Fixed Discount Amount in currency above: 1.55
Maximum uses per customer (0=unlimited): 1
To which plans this promotion applies: Your Plan

Advanced
Single payment (and for autorecurring payments subscriptions: First payment amount): No
For Autorecurring payments subscriptions only: Second and following auto-recurring payments amounts: Yes

It will charge them immediately, but they'll get 3 days discounted off the purchase price.

You should not unpublish a plan that is still recurring and used, but just set that the plan does not accept new subscriptions.