To answer your question, I think sets like the Heavy Hauler and the Passenger Plane have a limited future, especially with AFOLs. I bought both, but I can't justify buying many others (if any) like them. (Making the Heavy Hauler in green sold it for me, so depending on price I could be just as won over with next years plane. :-$ )
However, I don't think that Lego have made many pieces bigger than they used to, just the scale has changed. Aside from the trays, the Heavy Hauler has great and useful pieces, and with the plane it's just the nose, tail and wings. I do however think that Lego are more happy now to include bigger limited production pieces that make a set look more impressive at less cost. Aside from your examples, the bridge piece in 7900 and Sentai is a good example. Overall I don't think bigger is always better, and I think Lego is just trying to make sets more appealing to children and parents. I have no problem with Lego continuing down this path... but I hope it doesn't go much further.
While I agree with your first two examples, I think you are off base with the Armored Drilling Unit (7699). The 1990...
...version was much the same, and space generally did have big pieces in it.