Patch 5.3, like all new updates, is attracting a throng of returning players, many of which will be undergeared and willing to spend Gold to catch up with the rest. While the profits might not be as lucrative as with the new items, there may be less competition here. The key here is scanning the market for in-demand leveling gear and producing the right amount to avoid getting stuck with an unsellable stack of outdated items.
Mythic+ rewards will also go up by 30 item levels; however, during the first week of Season 2, rewards from end-of-run chests will be capped at Mythic 6 quality (item level 385), and the chest you open next week will contain Season 1 rewards if you do a Mythic+ run this week. (So, for example, if you do a Mythic 10 during the final week of Season 1, you’ll get a Season 1 item level 380 piece and 60 Residuum from your first Season 2 chest.)