Probably been a dozen similiar questions recently
http://www.flyertalk.com/forum/unite...-question.html
http://www.flyertalk.com/forum/unite...d-when-2p.html
http://www.flyertalk.com/forum/unite...s-expires.html
http://www.flyertalk.com/forum/unite...signments.html
http://www.flyertalk.com/forum/unite...-question.html
....
....
No clear consensus and some have reported loss of seats and others have reported no change. Seems a schedule or equipment change is a sure seat killer.

To guanrantee or make a seat chnage sign up for E+ annual access, talking to an agent without is likely to get you sent to E-
You of course can re-seat your self into E-