Luffy’s awakening will be simple. This is kinda rare.

Another awakened devil fruit user we have seen is Donquixote Doflamingo, who showed his awakened String-String fruit in the battle against our Luffy.

GOMU GOMU NO MI: THE BOUNCY HOUSE OF DOOM. It will be the ability to make the environment elastic to match his body. How is Luffy's devil fruit going to work in awakened state?

Theory.

They can affect their surroundings, on top of their own bodies, making their power something more than Paramecia really. Paramecia users like him, obtain the ability to transform the space around them, to that of their respective devil fruit.

Maybe trapping the opponents feet in the rubber ground. Devil Fruits are said to be the fruits of the Sea Devil and that the secret to their power is hidden in the Grand Line. THE DEVIL FRUIT AWAKENINGS FOR THE STRAWHAT PIRATES. There is a reason I started with this one and it’s because it is the easiest to justify. I've been thinking about it and I can't really come further than making the ground rubbery and bouncy. My personal speculation is that that his final form will be a mixture of gear fourth and gear second. After awakening, Luffy can still play around with the VASTLY improved flexibility of his devil fruit. Positive effects would be more jumping power and speed, softer landings, maybe forming fists and punching the opponent.

Because encounters with them are rare (especially outside the Grand Line), a number of rumors about them have risen, making it difficult to tell whether some things are fact or fiction; Nami dismissed them as mere myths until she saw the Bara Bara no Mi in action. As stated in the series, the fruits are classified into Paramecia, Logia, and Zoan types and each one of them can be awakened. Awakening is a special stage that can only be achieved by a few Devil Fruit users in the world of One Piece. Luffy would now be able to mix any gears, switch at any time, and incorporate Haki in any way that he wished. Awakening is the hidden ability of the Devil Fruit to fully use its potential.