+1 to both of these. We have a long way to see ICS working fully, let alone Jelly Bean. Keep this in mind as far as this is concerned:
The DX originally had Eclair. It was then bumped to Froyo, then GB. All these were considered the "incremental" updates to Android i.e. they weren't important enough to denote entirely new whole version numbers (2.1, 2.2, 2.3)
4.0/ICS was/is not an incremental update. It was arguably the biggest update/change to happen to Android thus far. Since we don't get official ICS, its a massive pain in the arse to get it working, as our phone was never designed for that, and its also why porting it has turned into such a headache. Anyone that remembers when either the Froyo or Gingerbread leaks came out, they were not that big of a deal at all to port. Sure, some early ports had some kinks, but for the most part stuff was 90% sorted within a month or two. ICS may never come that way, it just is dependent on how much longer this device will stay alive. Sadly, many original adopters are/have moved on, as we are reaching the end of our contracts.
The DX still has a few things going for it though - there still is a metric shit-ton of people who have the phone, being as Moto knows how to build a solid phone, and they can be had cheap nowadays on eBay/Swappa. If someone breaks their other smartphone or is looking to move up to a smartphone without a contract or on the cheap, the DX is a great option going for about $75 on eBay for one in good condition and a clean ESN.
Anyways, what I'm eventually getting at here is Jellybean is 4.1, not 5.0. So its incremental. Mostly face-lift type stuff with some new features. OTA is already out for it, SDK is getting released shortly. What this means for the DX? It depends on how many developers are sticking around. Jellybean may be port-able, especially as incremental so there's not necessarily the massive overhaul that's necessary for ICS. But its still based on ICS... its an incremental upgrade from it. So, we still need working ICS, to have working Jelly Bean, is what it boils down to. And Jelly Bean will just be extra work on top of the working ICS.
tl;dr NewmanX and Beans are correct. Get working ICS first, then focus on the jelly beans if the development force is still intact for the DX.