I think they'll do both i.e go ahead with the best partner to get a combo (that has a reasonable chance of beating ABT's 4-drug combo, at least on the adverse events side) to the market and keep developing a future next gen in-house one.
After spending 11B dollars (VRUS) my feeling is GILD wants to be first to market with an unpartnered drug in GT1. It would be so unlike GILD to think any other way. If they do "lay up" and partner a late-stage drug billions of dollars from warehoused patients would be forfeited.