Depends on shipping method:
Regular/Free Shipping - Yes, merged order placed in queue at time orders merged.
USPS Priority - No, merged orders with Priority are shipped per our Priority Shipping Policy.
When we merge orders, your "child" orders are replaced by a new order and a new timestamp. We process regular orders in the order they are received, and since the merged orders are "new" orders, they are in our shipping queue based on the time/date that the orders were merged. This does mean that merged orders are processed AFTER other orders that were placed at similar times and NOT merged.
The exception to this rule is for Priority Orders. If you pay for Priority, shipping on one of your child orders, your merged order will be processed per our Priority Shipping Policy and thus not lose its place in the order queue.