What class should Thrall reroll to

[Aeluron Lightsong]

I would say that he's more of a Monk than anything else, without the elements.

It would be odd but it does seem to match his ideals. This is assuming Blizzard themselves want to continue Thrall's story.

[Lady Dragonheart]

It would be odd but it does seem to match his ideals. This is assuming Blizzard themselves want to continue Thrall's story.

There's that and there's the fact that Thrall seems more like the type that just wants to settle down. Many Pandaren ideologies are relative to simply taking it easy and calming the stress that one has within one's self to achieve enlightenment and master the flow of chi.

However, yes, it is more likely that Thrall will simply retired much like Metzen, making the occasional appearance every so often, or so I would assume.