i can only partially answer you since i don't know any upcoming monitors
. as for 120hz vs high res, first of all at a higher res you should get ips, since you're not going to get 120hz anyway. e-IPS is a good one for price, with comparable colour reproduction to more expensive ips panels, and competitive/better input lag to lcds. other ips types will have more input lag, though those few ms probably won't make a difference - the price will.
games: "120hz and 3d" vs "more detailed small/further away objects, 2k texture packs, ips image clarity". 120hz is amazing, literally love it to bits, but it's good for the experience rather than performance. you'd have to be pretty good to see consistently improved shooting. 3d gaming supposedly has inconsistent support and opinions are divided on whether it has merit even when it works.
movies: "ips colour, viewing angles" vs "1080p native resolution, 3d". imo upscaling algorithms of today are severely lacking and inaccurate. call me picky but i really prefer watching 1080p to 720p with even the best upscaling methods. since you don't get >1080p films, you'd be upscaling all the time. 3d movies are called gimmicky, but for me it only improves hollywood/action type movies which i only watch for visual thrills and eyecandy anyway. 120hz does nothing for movies. also again, ips colour is supposed to be intense.
monitor size is down to preference and viewing distance. i'd get 23" 1080p or 27" 1440p. higher res = higher price, and i personally would hate to go back to 60hz. but people say exactly the same for ips to lcd, and having a bigger monitor would be pretty fun. it's completely subjective what you pick; take the features you prefer.
here's a suggestion: you could consider the yamasaki catleaps - up to 100hz, e-IPS, 1440p, 27". no 3d, but for those features it's a small compromise. from 100hz to 120hz isn't as noticeable as 60hz to 120hz anyway, and no gpu pushes 120fps all the time on every game. 100fps would be much more realistic, so you wouldn't see anything between the two a lot of the time.
