the new xbox coming out this year will have 4k 120 hz right ? or will it be 4k 60 hz?

I have a 240 hz pc monitor but that plays 1080p resolution and i also have. a 144 hz pc monitor thar has 1440p or 2k resolution .. i dont have a 4k 120hz monitor .. 4k 60hz costs around 400$ wheres 4k 120 hz costs over 1800$$ ...

Nothing has been announced for it yet. Wait until E3, then the specs and what it's capable off will be announced.

4k and 60hz are totally enough for me.

I would hope it would be capable of them all 👍

You have several setups.

This because the console, like was said above will support up to 8K with 120hz - this means that the
maximum performance, is up to the developers to use all that power, some will some wont. You gonna see some games supporting
8k/60hz, others 8k/100hz or 8k/120hz, or the ones that cant or wont use all the power will use like
4k/60hz or 4k/100hz or 4k/120hz.

I know like you said a 8k or 4k/120hz monitors or even TV's are a lot expensive for now, and if you cannot wait for the launch, for a xbox one X you should look for a 4k/60hz monitor, and if you can spend more try look for more hz. But yes for the series X
you will spend more money in a monitor or TV.