I recently purchased the Surface Pro 2 (SP2) in December 2013. After reading this thread I called back into the Microsoft Store direct to inquire as to why I did not get the most recent unit. The very helpful person on the line, Marina, took my initial Order information and the link to this thread. She put me on hold and did some research for probably 10 minutes. She came back on the phone and said that based on your order and the product, SP2 with 512 GB drive and 8 GB RAM, that you purchased (shown below) that you have the most recent processor that we have today.
Product Name: Surface Pro 2 - 512 GB
Product SKU: 7SX-00001
My CPU is the i5-4200 2.30GHz
They said that they no nothing about a faster unit in the SP2 as mentioned in this thread of posts.
Not sure, who to believe but that is right from the Store source.