Not really sure what you mean considering Samsung can pump out 4,000 phones a quarter. My only point was that an updated Thunderbolt Display shouldn't be hard to get into production for a company with the resources of Apple...even with the focus on iOS devices.
I mean, in a highly competitive consumer electronics market, we have not heard a peep from this company in 6+ months from a product standpoint! That's just odd.
There is such a thing as releasing products too often and it'll make investors/consumers upset. Imagine apple released a new iphone every 3 months. You'd be pretty pissed because they'd include something new in the newest one each time that you were missing out on.
Also consider if apple releases the new TB display today. A few weeks from now intel announces TB2 that increases TB speed by 2x, would you not be upset if you got one today?
Finally, the research and design that goes into these products does not happen overnight. Apple doesnt just say "lets make it thinner and lighter", they have to find a way to do those things efficiently and cost effectively. Then they have to make sure the facility that they want these produced at has ample equipment to make them as fast as demand, because if they dont then youll see another imac fiasco.
There are so many things that answer the "whats so hard" question you're asking. I prefer long drawn out updates that bring significant updates than a speed bump in the processor speed.