Of the people who are willing to drop 10k on a new <60" panel, which do you think sounds more appealing to them, 4k or OLED? Many here may appreciate the potential improvements OLED brings to the table, but I expect the majority of consumers don't. Factor in unknowns like susceptibility to burn in, lifespan, color drift with time, and a 4k panel may seem like a much safer investment. Then again factor in that Panasonic likely won't have anything to sell until the end of the year, then only in small quantities, if at all, and ask what the landscape will look like for 4k at that time. There will be more 4k available, and 1080p starts to look too "yesterday" for a large investment. I think the window is too small, will be filled by LG, and the cost is too high. I think skipping 1080p OLED is probably the right choice.
You can't say off-hand "why not just incorporate the added cost of 4K", as if that's some off-the-cuff ignorable nut to crack. Look at what just "incorporating the added cost of 4K" does to the price-tag of a technology we already DO understand.
You can't equate the price tag with the cost of production. If a 4k panel costs double to produce compared to the cost of equivalent quality 2k panel, in the early stages it could still sell for 4x the price.