I can't speak on Icom, I haven't owned any of their radios in quite a while.
I do run a NexEdge trunked system and have over 400 Kenwood radios on it. About to add 50-60 more radios and an additional trunked site.
Kenwood recently rolled out NexEdge Gen2, so there is still active investment in it.
They've also rolled out the NXR-5x00 repeaters, including just recently, an 800MHz and 900MHz version.
There are cases where NXDN trunking scales better than the DMR options, although I suspect there will be an ongoing leap-frogging of the two.
Kenwood has been building/selling DMR for quite a while. They only started offering it in the USA a few years ago, but they've been in the market for a while.
Kenwood's move to offer DMR is likely (read: my opinion) more based on gathering market share than trying to compete against it's own products. Kenwood is well placed to take a seat at the big table, and has already in many areas.
Kenwood is going to offer Tier 3 DMR in the near future, from what I've read, so they'll have DMR trunking as well as NXDN trunking.
They are similar products and are aimed at a similar market. What happens in the long term (read: 10 years or more) will be interesting to watch. I don't see that Kenwood has any plans to do away with NXDN any time soon. Considering the railroads are starting to move that was in -some- places and they've chosen it as their standard suggests there will be a market for it for quite some time to come.
Like I said, it'll be interesting to see how this plays out, but it'll be a long term thing.