Yes but the default functionality (as it has been since Broadleaf 3.0) is to not merge but just overwrite. This is how it works:
1. User is anonymously browsing the site
2. User adds Item 1 to their cart
3. User logs in
4. User still sees Item 1 in their cart
5. User logs out
6. The user doesn't have anything in their cart (they don't actually have a cart yet)
7. The user logs in
8. The user still sees Item 1 in their cart
9. The user logs out again, no items
10. The user adds item 2 to their cart
11. The user logs in
12. The user sees only item 2 in their cart and they have a wish list that contains item 1
Basically, the active cart is always the current one. Any other cart that the user has previously is saved off as a dated wishlist (NAMED order).
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