This is assuming you get the device
today (you used the current difficulty, well, almost).
LTC has had its difficulty increase by about 60% the last month, so assuming this rate continue until the time they deliver their miner, you can expect a difficulty of about 14,750, which means your ROI is 54.58 days.
And TBH, 2 months ROI with this is almost guarantee that you won't see ROI at all or barely make any profit.
This of course doesn't include LTC price change (up or down).
however one question I have is how are they going to make any new coin asic resistant, if these can mine any scrypt coin out there?
Scrypt is Scrypt and it represent just a certain algorithm. Any coin currently that uses it can be mined with said miner, but coins that are based on different algo can't be mined with it.
another would be, how can you tell knc will premine these units? did they premine with all their other units? I know they had to for testing.
Don't think anyone can answer you that unless they worked at KnC at the time. But when you think about it, and not even that hard, it's the only logical move from a monetary POV.
They are in the business of making money, and to maximize profit, they should mine with the miner themselves and than sell it.
And please don't bring up the gold rush / shovel sellers analogy, it's so retarded and completely irrelevant to cryptocurrency and how it works.
Was there a spike I didn't catch, just before they began shipping them?
You don't need to see a spike as obvious as you imagine. They could easily just add a single miner to their farm once a day and you'd never see a sudden spike in network hashrate. You would however, see an increase in hashrate similiar to an exponential growth graph.
Keep in mind that you will need to add up the total network of all Scrypt coins together in order to see it.