Hi Carlos,
Online migration from your existing P2000 G3 to a new MSA 1040 or 2040 should work fine as we do support 6Gb SAS drives in both platforms. One of the hallmarks of the MSA family has been what we call "data in place" upgrades that allow you to move drives from generation MSA to a new generation.
Here's a link to the upgrade white paper: http://www8.hp.com/h20195/v2/GetPDF.aspx%2F4AA4-6830ENW.pdf
I have not personally done the data in place upgrade myself so be sure to talk to your HPE rep or channel partner before you proceed. Lastly, I'm as I type putting the finishing touches on a blog post talking about what's new with the MSA. . It should be live in the next 30 minutes or so as I'm just checking for typos.
Let me know if you have more questions.