I would like to see less horizontally and more vertically, because my current setup is a little too wide. I just want to make sure I'm not losing overall real-estate and that the text is not going to be miniscule.
I went through some of the same thoughts and wants as well, but I ended up keeping my dial 1080p setup at the moment. Here's some things to consider:
I tested the Dell 34" ultra wide as replacement for my dual 24" 1080p monitors. It was just a little bit less wide than the dual setup, but overall fit the space pretty well. Where I struggled was that I was so used to having two separate displays that I couldn't get used to having one large display with my various programs running on it (keep in mind this was in Windows). While I'm sure there are a plethora of programs that can help you carve up the space on the screen to dedicated programs, my work routine is too heavily engrained in my mind and muscles that the wide open real estate of the screen was just too hard to wrangle at the time.
Prior to that I had tested one of Dell's 27" 4k screens. This seemed like a better option since I could do two side by side, still keeping my separate work screens, and get the benefit of 4k. At the time I just didn't care the color uniformity (had sections of yellow) and returned it.
From the work side, I still use the two 24" 1080p monitors and they are fine. I did buy a 40" 4k TV for my personal PC rig that also sits on the desk next to the dual monitors. My work laptop can only drive a single 4k monitor (max), so I don't use it for work, but I do use it for gaming and anything being done on the personal PC. Text and everything looks great (make sure you buy a 4:4:4 4k TV for the best text resolution). Admittedly, I don't use this setup for reading or documents, but the time I spend doing updates and hitting URLs, it looks good.
If you go 42" 4k, how far back will you sit? I sit at least 4-5 feet away from my 40". I worry that, for how you want to use this 4k screen, you will be right on top of it, and for me, that would just be too much screen in my face all day long.
My final thoughts are, just because it provides all the pixels you think you might need, its a whole different experience sitting in front of something that big (and close enough to use that real estate for productivity). I personally sometimes find it overwhelming.
One other thing I tested was a 4x24" monitor setup (two x two). That actually worked probably the best for my needs giving me 4 distinct screens to put things in. With the ultra wide, RDP would open sessions with the max resolution (I eventually set it to default only to 1080p), but even then I had to move the screen around all the time.
Anyway, I would say definitely test it out. if you can. My 40" Samsung 4k 4:4:4 TV was only about $500. Cheapest 40"+ 4k 60Hz monitor out there...
