Can't see this happening myself.
In this off-season Porter was handed a $7m signing bonus over 5 years.... witha cap charge of $2.4m this year (1.4 pro-rated signing bonus and $1m salary)
If the Raiders do trade Porter, the cap charge increases to account for the full signing bonus of $7m (an increase of $4.6m). Couple that with what Owens is expected to make as a base salary in the present deal, some $3.25m (and that's before he has renegotiated!!!!!) and you are talking about to get Owens to play for you a cap charge of $10.25m.
Now the boy Snyder might consider a deal like that, but I doubt Al Davis would.