Re-platform effects on Page Rank

[Bucktown]

We are performing a major replatform for an ecommerce client who has many top listings on page 1 in Google SERPs for very competitive terms.  We are implementing a 301 redirect for all existing URLs that they have now to the appropriate new URLs, but the client is concerned with how deploying a new site with 100% new URLs and site structure will impact their Page Rank.  From our experience, the 301 redirects should cover it but wanted to see if there is a way to predictively forecast page rank effects as a result of re-platforming.

[EricaMcGillivray]

301 is the best solution possible. Many people have asserted that you can see up to a 10% dip initially. (Most people only see dips from a week to a month at most.) However, over the long-term, with a better site & URL structure, you should see a rise in traffic. I have no seen anyone doing a predictive modle on this.

Seer Interactive did this test 301 Redirect Test: How Much Link Juice are YOU Losing? which saw no rankings lost, but favorable outcomes in the long-term for the better site.