That's a good study that just proves what I have said before: if this debate is done in Western Europe or in Northern Europe, I definitely agree that it is necessary to have a serious collective decision on limits to immigration because the society and economy just can't integrate and assimilate so many people so rapidly, and this could trigger increasing problems, HOWEVER it's also demonstrated that many Eastern European states where panic against immigration is even higher than in the West are being really over the top and choosing it as a convenient priority to divert people's attention from much more structural and chronic problems that are entirely internal (and, of course, are inconvenient to powerful politicians because they were caused in a large part by the policies enacted by those politicians in the past). Those countries who are leaning to the right in worrisome ways are not Sweden or Germany, they don't experience any significant population replacement AT ALL, and all the objective data confirm that (those fantasy scenarios of agenda-driven nutcases don't matter).
Poland is estimated to have 0.2% of Muslims in 2050, the Czech Republic 1.2%, Hungary 4.5%, Romania 0.9% - and that is in the HIGH MIGRATION SCENARIO (which the study itself acknowledges that is most unlikely because it assumes that the rat of the record years of migration crisis will simply go on indefinitely). If we consider the MOST PLAUSIBLE scenario, which is the MIDDLE one, the numbers are even less conducive to all this sensationalist panic: 1.3% for Hungary, 1.1% for Czech Republic, 0.8% for Romania, 0.2% Poland.
Oh the barbarian hordes are coming! - just not. Meanwhile, I'm sure those nations have much more pressing and, even worse, structural issues that they aren't simply discussing much at all how to solve while they still can before things get more complicated and, hopefully, even before they suffer the worst consequences of their alarming demographic decline.
One doesn't have to be a genius to notice that, in this matter, Hungary and, even much less so, Poland aren't remotely comparable to Sweden or Germany. One also doesn't have to be a genius to notice that France, which has the highest Muslim population now, is supposed to have less Muslims than other countries in 2050, for the very simple reason that the French people as a whole still has a moderately sustainable pattern of fertility, birth and death rates. They are still willing to make families. But for some other nations it's better to pretend that there is "no social and economic problems" at all with their countries' socio-economic system to make fertility rates drop to as low as 1.1.