Regarding CB, I wonder what people expect exactly.
Nixon's performance dipped this year, but still was rated as a starting CB. Saying he is league average is a fair assessment. He is on a decent contract for his performance, so not much to gain by releasing him either.
Valentine is on a rookie contract which basically is enough to say he stays. Performance wise, I'd rate him about the same capability as Nixon, but worse on instincts. There were several coverage blunders where he looked like he was guessing and got burnt.
The chances of both of them coming back are very high.
Hobbs' return could be debated. I'm about 50/50 if I think they will give him a second try or not. Mainly because there isn't a lot of cap savings to be had (although there is cash savings).
But either way:
Nixon, Valentine, (development CB holdovers from last year) + draft pick(s) + a FA
or
Nixon, Valentine, (development CB holdovers from last year) + draft pick(s) + Hobbs
neither would constitute wholesale changes... Doesn't sound like there is much available for FA signing either.