H1-B Transfer to new employer in 6th Year

[fusebox]

Hello Folks!

Below is my current status:

1) H1B with Company A will be expiring next year Jan 2014.

2) My perm was approved in March 2012.

3)I-140 is currently still pending approval..

I got an FTE offer from a different Company B recently. Speaking to their immigration lawyers, they said that since my perm was approved prior to me entering the H1B 6th year, they will be able to do a H1B transfer to their company with a 1 year extension based upon that perm until Jan 2015 and they said they will be filing for the GC as soon as the H1B transfer is done.

Forum members, please advise if this is possible like the lawyers said and are there any risks involved for me in this if I go ahead and take this job offer with company B?

Thanks in advance.