The truth is that it makes no sense to sell it off right now. Loss and cost of aquiring new vehicle may not recoup any gas savings. If you shop for new you may want for something more economical, but I do not see any practical reason one would have to rush to get rid of their 300Cs.
Gas prices are one of the reasons Lincoln decided not to put V8 into their upcoming MKS. MKS is a very nice car in my opinion, but lack of V8 option creates the feeling that something is missing. Though these perceptions may change over time.
However, I have got hooked to V8. It will be difficult to go back. I tried CTS with 3.6 DI which comes close, but still does not feel the same solid and strong as HEMI. MKS's V6 is not even as powerful as powerful as the one in CTS.