Green has never been very good when asked to play PF, though. And, we really need a starting-caliber PF more than a SF, since I don't think Pierce is going anywhere.
And, it all comes down to dollars. Green and Bass are both good, but if re-signing them prevents you from being able to add an impact player, you give them a hearty "thank you!" and drive them to the airport.
If Green and Bass come back cheaply and/or on short deals, great. Don't think that's happening, though.
If Green and Bass come back and we've basically burned our cap space on them, that's the worst outcome.
And, I don't think Bass is any better than he was last year (his numbers are nearly identical), which makes me think he's not likely going to get any better.