From Sideshow at SDCC 2012 via Rebelscum (Question to Sideshow's Brant Bridges following Sideshow's presentation at the Star Wars Collecting Panel):
Q: 12" Indy figures at Sideshow?
A: Yes! Short Round, maybe some Temple of Doom figures.
Nothing close to concrete, but it was not "NO" or even "on hold for now."
Next year is the 30th Anniversary of Temple of Doom and honestly, what would Hot Toys have to do that is new for a TOD Indy release... a head, a machete, a torn shirt, maybe a tux?
TOD Indy is the only other "iconic" look for Indy beyond what they have done.
The last release coinciding with the 30th of Raiders was a DX figure from HT, and an environment from SSC that went with it. The mine cart is presumably the environment intended to go with a HT TOD Indy, with a Short Round fig included to sweeten the deal.
But yeah, development of the Mine Cart has been anything but linear and rapid...
Aug 2010 - SSC states Mine Cart "in the works",
Oct 2010 - Shorty figure has "started development"
Sept 2011 - Shorty figure has "hit a snag" due to smaller body problem.
July 2012 - SSC states emphatic "yes" when asked about Indy figures at SSC, citing Shorty and other possible TOD figs