I think you may be right. But its not a slam dunk. While the complexity of the injection stuff is undeniable there are advantages even on a pure dirt bike (but probably not for a motocrosser) like increased range, no flooding when the bike is on its side, no messing with jets AT ALL, no pinging or blubbering, yada yada. Right? Potentially the power band would be superior and perhaps with higher peak as well.
As stated by others, all this stuff has been made to work on other platforms with extreme reliability. The challenge on a dirt bike is the sheer cleanliness required and the pounding the components will take. Much more than on a snowmobile or an outboard on both counts.
Even with DI/FI stuff on it a two stroke engine STILL would not have cams, valves, springs, chains. And would still make far superior HP per CC. I have to believe that mass produced FI equipment has to be cheaper to manufacture that all that precision machined valve gear nonsense. You still would be able to pop the jug off in 20 minutes. The advantages remain.
Without this I feel that the two stroke may be a dead end for our dirt bikes - in the long run. Unless something big happens (or AMA/FIM change the rules back to what they should be), and the Euro regs are as you say there really is little reason to continue making them from a bean counter point of view. KTM somehow has the wherewithal to keep development programs going for both 4T and 2T. How long can that last?
Keep dreaming because you aint ever going to see a direct injection two stroke dirt bike, for a host of technical and cost reasons.
EuroX emissions targets are NOT based on the individual models but are calculated across the entire model range, the idea being manufacturers can still have thirsty sport/competition models that don't meet the targets but the everyday commuter vehicles are well under the target so on average it balances out.
So there is not a single reason manufacturers would spend a gazzillion Euros to make a model compliant when they can make an existing compliant model further under the target