For now, the LG UltraFine 5K Display is the best alternative to the Thunderbolt Display, and it comes with a 27-inch display that can support resolution up to 2880x5120 pixels.
Taking a quick look at customer reviews for this monitor on Apple's website reveals that quite a few people with this monitor bought it with the intention of using it in close proximity to a wireless router.
You can find several reviews on Apple's site complaining about this problem, but 9to5 Mac's Zac Hall recently gave us a front row seat to this issue. Apparently the UltraFine 5K Display will flicker, disconnect, or freeze computers due to electromagnetic interference. This certainly seems like a major issue and plenty of customers are complaining, so it is only a matter of time before Apple acknowledges the problems and takes action.
If the router happens to be within 2m distance of the display, then the monitor isn't so "ultra-fine" - in fact, things aren't remotely fine, and the peripheral becomes effectively "unusable" as 9 to 5 Mac reports.
Hall performed a similar setup, testing his display in another room, which worked. The root cause for the interference is now unknown, but poor shielding could be at play.
LG recognizes the problem in an email to 9to5Mac (see screenshots below).
LG's technical support acknowledged the problem, advising to check whether the monitor is near a router, and saying that this could affect the performance of the display. If you can not move your current workspace that comprises up of the 2016 MacBook Pro and the high-resolution display, then your only other option would be to maintain a distance of 2 meters from the router and the monitor. Could this be a blunder in the product's engineering, or an isolated case?
However, the UltraFine 5K seems to have a rather serious flaw. Without more 5K monitors on the market to test, it's unclear if this limitation will be hardware specific or an issue in all external 5K displays coming soon.