I think Sideshow's biggest mistake was announcing Indy on the new body, without a definite lock being in on when that body would be ready. I could be wrong, but I can't see what else would be holding this figure up for so long. They should just have announced the figure, and if the prometheus was ready in time to ship with Indy, then by all means do it - if not, put out the figure on the buck and at least capitalize on momentum, and maybe release a different film version of Indy on the new body later on down the line.
Of course not all of this is Sideshow's fault - I think they were hoping KOTCS would restart the Indy franchise, and while the film was financially successful, critics were divided, and even though audiences seemed pleased, it hasn't lingered in the public consciousness. So I guess what might have been planned as a much more comprehensive assortment got aborted pretty quickly, with Belloq released at least as an attempt to recoup some of the R&D costs, and the environment bundled with him to make an otherwise ho-hum looking character attractive. My gut feeling is that Belloq was originally planned as a filler character to keep enthusiasm alive between Indy and other "wow" character, but production delays and lower than expected sales of Indy merchandise industry-wide has brought this line to a premature end, before that "wow" character could be got to production level.
Bottom line, though - Sideshow should have had 3 or 4 characters able to go into production within 6 months of announcing the license, and at least two of them should have been more than just a guy in a white suit. That way they could have looked at how Indy himself was selling, and released another character that would either increase interest if sales were slow (eg Mola Ram, Toht, Henry Snr), or maintain it if sales were fast (eg Belloq, Donovan).
How ironic that a figure due to debut a body named after someone who created and gave life to men of clay, and stole fire from the gods to give to man has fizzled out so lifelessly!