Has to be a way to extend for 2 more years, making his contract a 3 year contract. Lower his cap number next year, but puts some guarantee money into the contract. Then Forte can either be a #1 or #2 option, doesn't mean the Bears shouldn't still draft a RB to compete to take Forte's spot. Best case scenario that is realistic is that Forte signs extension lowering cap number allowing the Bears to commit money elsewhere, and Bears draft a RB. Forte is #1 option in 2015 with draft pick and Carrey getting some carries. In 2016, Forte will still have a reasonable cap number, and will losing carries to the other RB's on the team not because Forte is horrible, but because they are making plays. 2017, Forte is still healthy, just has slowed down. Can still catch out of the backfield and pass-block well. In 2017 Forte only gets on the field for about 25% of the offensive snaps.
Of course, if for some reason a team offered the Bears a trade, say a 2016 2nd round pick, I hope the Bears would agree.