Technically you will only be entitled to the benefits of your current status.
However, if you don't change your booking at all and don't change your seats it is possible that the seat assignments may stay.
The luggage benefits I would be less convinced would remain.

You will be boarding group 2, along with all of the passengers on the same booking.
You may all use the business class check in but you may only guest 1 other person to fast track security and the lounge.

If you post your dates on the travel meet-up thread you might be lucky.
I don't really post where/when I am travelling but I do keep a look out for other FT-ers to meet-up with, as do many.