Everton boss Roberto Martinez would dearly love to make the Belgian's stay a more permanent arrangement following a hugely successful season-long loan from Chelsea, but the striker is sure to have plenty of high-profile suitors.
He was the stand-out performer in Everton's win over the off-form FA Cup finalists, involved in James McCarthy's ninth-minute opener before showing power and poise to double that lead just after half-time, and otherwise cause the Tigers all manner of problems.
For the hosts, an impressive return to the top-flight ends on something of a bum note with just one win from their last eight fixtures and four points from a possible 24.
Steve Bruce's side still have a first-ever cup final to look forward to against Arsenal next weekend, but they will need to be significantly better than this to compete with the Gunners.
There was some good news with Allan McGregor and Paul McShane both coming through comeback matches to put their names in the hat for Wembley, but both could have done better for Everton's goals.
Everton left World Cup hopeful Ross Barkley out of their squad, along with John Stones, but they did not miss him in a neatly crafted opener.
Sylvain Distin played the ball forward to Lukaku, collecting with his back to goal, before laying off to Steven Naismith, who spotted McCarthy appearing on the overlap.
The Irishman connected well but McGregor was well-placed enough to do more than parry it into the far corner.
For McCarthy, it was a first goal in 39 matches since arriving from Wigan.
The away fans celebrated heartily, though that was not a patch on the roar they mustered when news filtered through that rivals Liverpool had gone behind to Newcastle.
Hull had half-chances to go level, Phil Jagielka's back-pass almost gifting former team-mate Nikica Jelavic a one-on-one and Sone Aluko driving over from 20 yards.
Everton's promptings were more threatening, with Gareth Barry more involved than usual in driving the side forward.
But the finishing was less than clinical, Naismith side-footing wide and Lukaku scuffing a first-time effort, both from good positions.
Hull appealed for a penalty on the half-hour when Lukaku, stationed on the end of the wall, appeared to move his arm towards Jelavic's free-kick but Howard Webb was uninterested.
The hosts were certainly struggling to get the job done from open play, with Tim Howard only kept interested by a pair of low drives from Maynor Figueroa.
Everton might have nicked a second before the break when McCarthy's cross was deftly turned goalwards by Lukaku, but McGregor was alive to the danger.
Lukaku did not have to wait long for his goal, with the second half underway only a matter of seconds when he picked up Leon Osman's through ball, shrugged off McShane and fired home.
For McShane it was the kind of moment that bodes ill for Wembley and, with his comeback cut short in the 62nd minute, he faces a nervous wait.
Jelavic has no such uncertainty over his place having been cup-tied earlier in the season and he was replaced in the 54th minute by Matty Fryatt, his likely stand-in next weekend.
His arrival prompted the home contingent into a chorus of 'Que Sera Sera' but on the pitch Hull were looking like anything but potential cup winners.
With little else of note happening it was impossible for minds not to drift towards the final, not least when Hull's player of the year Curtis Davies hobbled away from a coming together with the muscular Lukaku.
Fortunately for Bruce, who had pondered resting the 29-year-old, he was soon back at full tilt, almost scoring from a corner late on.
The end-of-term feel continued when Bruce handed club captain Robert Koren a 17-minute cameo in what seems likely be his final appearance at the KC Stadium, but he could not lift the Tigers
Source: PA