Gizmo1,
The first question to ask is what sized TV are you thinking of buying and what is the distance at which you plan to view your TV ? The ideal resolution is a factor of both of those items.
Secondly, as has already been hinted at, you might find there to be a limited number of 4k sources. Upscaling existing HD content to 4k will not enhance picture quality, you can't polish a !!!! but you can sprinkle glitter on it !
Finally, yes I would think curved TVs are a bit of a gimmick .... but I've only seen them around the shops, have not actually sat in front of one for a period of time....
If I were you, I would probably look at buying a top of the range HD TV instead ....