Whether it's a "#1 WR" like a Holt or Bruce or not, "receiving threat" is the key. Receivers the defense respects and has to account for every play. Receivers that prevent defenses loading up the box vs. the run. I do think Higbee could develop into that guy. And if he does the unpredictability of the offense goes
way up, regardless of play calls.
I also think Higbee and Spruce together could be just what the Rams need to solve for their horrific 3rd down conversions rate. Not to say we can count on plugging in two rookies to do that, but in the longer run I think they can.
Austin is already a threat. He's just not enough by himself.