[Tuor in Gondolin]

There's a not uninteresting argument in TheOneRing.net for
a cameo by Orlando Bloom in TH.

Why Orlando Bloom
should be in ‘The Hobbit’

Although the author seems
under the misapprehension that Gollum was confined in the
dungeons (not up a tree) in Mirkwood.

An excerpt:

So while Legolas had no explicit role spelled out in the text, Princes of Mirkwood wouldn’t miss events like the notable capture of Dwarves or the restoration of his father’s honor and kingdom via war.

Now if it were up to me, Bloom would probably not speak a word in either of the two Hobbit films but would stand behind Doug Jones Thranduil silently supporting and honoring his father. He would definitely be present at the flicks’ biggest battle doing low-key but unmistakable Legolas moves.

I don’t know that Bloom would agree to a part with no dialog but if he would it would be a classic nod to his non-mention in the books while providing a line of continuity from del Toro’s films to Jackson’s. It wouldn’t require a large time commitment either and would likely delight studios and financiers. It wouldn’t be an over-the-top, distracting cameo but a tasteful, clever and humorous walkthrough that would also feel just ‘right’.