As I understand it here are some of the main obstacles to bringing FP+ to DLR:
1. Space - WDW added FP queues to almost all the rides. DL has limited space for that. DCA has a bit more space. But DL will be tough.
2. Visitor mix - something like 70% of the DLR visitors are day trippers from SoCal, many of them AP holders, many of the AP holders there for only part of the day, and many of all of those folks make decisions to visit DLR on a whim or at best just a few days before they actually go. Many of the local SoCal folks will choose a day to visit based on the weather. Super hot? Wait and go next week. Cold or rainy? Wait and go a few days later.
3. General culture - DLR visitors are by and large not big planners like WDW visitors because they are for the most part not on a big, expensive family vacation. Part of the reason why dining reservations at DLR are in such low demand. Visitors do not really care to make a detailed plan. Many hop back and forth between parks on a whim.
Will FP+ come to DLR? I think that depends on a few things...
- Money and return on investment - Can WDW show that FP+ is actually making money for Disney. As I understand it that was a big part of the justification in that they could make more money and keep visitors at WDW. If they can't show they are making more money at WDW I do not see why they would go through the expense of bringing it to DLR where they would lose even more money.
- Location and influence of decision makers - it seems like sometimes the folks in Florida make decisions that get applied to DLR without understanding the differences between DLR and WDW. Sometime the folks over DLR are able to be heard by the decision makers. Depending on who wins this debate may influence if FP+ comes to DLR.
Bottom line? I think it is likely FP+ will come to DLR at some point and it will not go over well because of reasons 1-3 above.