I had to stay up to post the announcement, as it was embargoed until 00:01 PST (which is 03:01 my time), so I'm going to make this quick (as I'm falling asleep at my keyboard here).
Comparing the UE18 Pro and the JH13 Pro is fun, as they're different. From a purely selfish standpoint, already owning a JH13 Pro, I was hoping that they'd be different, and, again, they are.
The low midbass is a somewhat more emphasized with the UE18 Pro than the JH13 Pro, giving the UE18 Pro a little more thump. The UE18 Pro's presentation sounds more forward to me, with thicker, more emphasized mids. Both have outstanding high frequency performance (UE claims extension to 18 kHz, JH Audio to 20 kHz)--but the more neutral bass and mids of the JH13 Pro makes for even more treble sparkle from the JH13 Pro, on balance.
The JH13 Pro is comparatively more neutral, no doubt, and sounds to me like it is more geared toward audiophiles than the UE 18 Pro is, the latter with its warmer tonal balance. Prior to the arrival of the UE 18 Pro, I had been carrying the JH13 Pro and UE11 Pro around with me almost everywhere, the JH13 Pro getting significantly more use since its arrival than my UE11 Pro (or UE10 Pro). I've since replaced the UE11 Pro for everyday carry with the UE18 Pro, and it has been getting about equal play time as the JH13 Pro in my rigs.
To my ears, until the UE18 Pro arrived, the JH13 Pro was simply technically better than anything Ultimate Ears had in their stable. The UE18 Pro, based on what I'm hearing, closes that technical gap, yet offers a different sonic flavor than the JH13 Pro. And it doesn't take gobs of listening to come to the conclusion that Ultimate Ears was undoubtedly shooting for a different flavor with the UE18 Pro (than the JH13 Pro)--I think if they ever decide to aim directly at the JH13 Pro, we'll hear more similarities then. (And, no, I know of no other upcoming models by UE.)
Even before they contacted me, I figured UE wasn't sitting still. Truth be told, I pretty much knew the call was coming, I just didn't know when. When I heard the UE10 Pro for the first time (in 2006), I wondered if IEMs could ever get better than that. I think it's clear no major player in this market is sitting still at all.
This is an insane time to be a Head-Fi'er.