As far as I know I believe both will be restricted free agents and with most teams trying to clear cap space for 2010 I can't see at this point teams offering contracts that we won't be able to match. There will actually be a number of good free agent big men next year so if we happen to lose Powe or Davis I feel confident we could find a decent replacement.
Here are some names that will be unrestricted free agents Zaza Pachula, Drew Gooden, Brandon Bass, Chris Anderson, Rasheed Wallace, Rasho Nesterovic, Chris Mihm, Lamar Odom, Antoine Walker, Jamaal Magloire, Shawn Marion, Stromile Swift, Melvin Ely, Malik Rose, Mouhamed Sene, Joe Smith, Robert Swift, Adonal Foyle, Theo Ratliff, Raef LaFrentz, and Shelden Williams. There are also players who will be restricted like our own 2 big guys like David Lee, Paul Millsap, Johan Petro, Charlie Villanueva, Hakim Warrick, Paul Davis, Josh McRoberts, Aaron Gray, and Sean May. I might have missed 1 or 2. Say if we lose either one of our guys in free agency there couple names here that we could go after like Joe Smith but if Ainge really wants both guys back he might be able to do it at a reasonable price.