I honestly don't think any further upgrades are needed between Macomb and Jacksonville, nor between Manchester and Jerseyville. At this point, I'd simply four lane the Macomb bypass and tie it directly into US 67, then call it a day on US 67/IL-336 upgrades in Western Illinois.
IDOT's priority should be reconstructing and widening I-55 around Springfield to 6 lanes with a redesigned interchange at Clear Lake Ave that replaces the cloverleaf with a new one that allows I-72 traffic to free-flow on and off I-55.
I'm not sure Jerseyville needs a bypass since I assume most traffic on US 67 between Jerseyville and Godfrey is from Jerseyville anyway.
The main reason why US 67 probably won't be expanded between Jerseyville and Manchester and west of Jacksonville to Macomb is that west central Illinois is losing population and most long haul truckers drive on the interstates unless their destination is far out of the way like Macomb. About the only thing I expect to happen other than 4-laning US 67 to the southern part of Jerseyville is a new bridge at Beardstown.