The more variety you have on the auction house, the more markets you can capture. Now that each expansions profession can be levelled separately, many will have skipped the old stuff and just focus on the latest expansion. It might be certain enchants for levelling or some hard to get crafted transmog that might just be the set piece for an ensemble.
There are still many crafted things that sell to other players.
Now would be the perfect time to fill out professions from older world content. U/RookJackson has some great advice here and we can expand on that further into things to do right now as regular commodities steadily drop in price. What professions will you want next patch? Do you need another character? Is there any hard to get patterns you're missing? Is there anything non-goblin you want to do for fun? When patch hits you likely won't have time for this, so it's a good time to get started. Since material costs are getting cheaper and keeping up with sales is easier, it's posturing time.
