TLDR:

Upgrade fast, farm fast, sell fast.

I think of the followings:

1) Better Co-op games & A1 Density
2) Gold Dupe bug at SC

1) Better Co-op games & A1 Density

Better efficiency in killing, additional MF per additional player, higher density in A1 for fast XP = faster P-leveling, better MF farming.

Most importantly it is safer in co-op than playing solo = less RIP = less gold sink, more farming with high P toons instead of rerolling.

Long term effect = decent items start getting cheaper due to more supply. Uber item possibly inflates in value.

2) Gold dupe bug at SC (fixed......)

This probably brings more awareness of value of economy at hardcore. Hence possibly more players now switching to hardcore. Hence more supply of items in the long term (if they stay, if they stay alive!).

Could be some short term effect from people who convert SC golds to HC golds. They are not creating new hardcore golds but some of the hardcore golds which were stock are now in the hands of new players who wanted to quickly buy things off AH and start farming (then they either survive and start supplying more items & gold, or due to inexperience they contributed to gear sinks and maybe never return again). These converts have been happening all the while, but there could be fewer people willing to convert HC:SC golds now since the SC dupe bug, unless for a very good ratio.