Unless something has changed, Luka is not on any mock draft boards. I don't know how all that works, such as if a player isn't listed if it's assumed they return to school, but I have yet to see anyone projecting Luka to any team. Has anyone else?
Regardless, I believe Luka when he says he'd have to be presented with a "real opportunity" before he'd pull the trigger on forgoing his senior year at Iowa. If Luka were Kevin McHale's age, forget about it. It would be a done deal. But that era is long gone, as is the era of 2nd Rd picks like Jeff Moe and JR Koch.
Unless someone has a compelling reason to suggest otherwise, I'm guessing Luka will be encouraged to stay at Iowa to work on improving his athleticism and outside shooting. I have no doubt there are NBA teams who'd be willing to use a 2nd Rd pick on him this year, but I highly doubt any team, if being honest, has told him they expect him to compete for a spot in their rotation this upcoming season, which I believe, if reading between the lines, is what Luka is saying it would take for him to make the jump to the NBA this year.
So, in my completely un-expert opinion, I believe Luka will be returning for his senior year at Iowa.