You don't say why you want to spend money swapping one 27inch monitor for another, other than 4k.
In what scenario is 4k needed?
Running a 4k desktop is just going to make everything smaller and harder to see.
If you are editing 4k video you really need a second monitor to display your video output while the timeline is on the other.
If you are talking about viewing high res photos 1-to-1 on it, then the pixels are going to be so much smaller that there will be no real advantage for pixel peeping over using your existing monitor and zooming in to check details.
If you watch 4k content from Netflix/Amazon then you still aren't going to get the best viewing experience because effectively you're watching a smallish tv.
If you have money to spare, then why not. But if you'd have to sell the current one and find additional money in order to get it, then you do have to question your reasons.
I work in broadcasting and I'd say that only half of the industry is interested in 4k and that's those working on high end drama and docs (and half of that is only to future proof the content). The rest of us aren't bothered yet, either for video or graphics editing.