I've always wanted them to do this, but I think it would take an arrangement that either Hasbro is unwilling/can't afford to make, or is unable to within the terms of their license. Here's how I figure it:
Scenario A: They make a Sail Barge, Death Star, etc as an ultimate collectible for 3-3/4" scale, and the pricetag brings it in at say, $150-$200 retail. Hasbro can't move enough of them even through an exclusive retailer arrangement because of size/cost. If they had trouble getting the shuttle out using existing tooling, they'll never be willing to shell out the development costs to make an all-new vehicle/playset happen.
Scenario B: They move it online with the same specs. They once again most likely run into order numbers that don't come close to justifying the expense of development, manufacturing, etc.
Scenario C: Sublicense. This would require that their master toy license from LFL allows such an action, which it may not. More than likely they hold all rights to toys, and any portion that they do not wish to pursue can not be sublicensed, but instead would need to be relinquished to LFL, which in turn could license the category to another company. And I'm sure Hasbro, even with the notion of never, ever releasing something called a "high-end vehicle/playset" line, won't let someone else make one without pulling some profit off it. So, it never happens.
Which is a bummer, because what would be great is a sublicense where a smaller shop, Neca, McFarlane, whoever, or a brand new company, fabricates the toy to awesome collector specs, and sells in limited numbers to the small collector base that wants the item. I'd figure under that scenario a Sail Barge, done right, would be in the $200-$250 range.
EDIT: My point is that I don't believe Hasbro is the company that can focus their efforts on a line like this. They're too big, too mass-market, and bandwidth-limited with other parts of the line, like Ep3. There needs to be a subline that compliments the main line to make this happen, and I don't see it ever happening.
This has been another pessimistic post by Jared. Thank you.