Don't forget about Georgia and Belarus. And possibility of internal shenanigans with Latvia's Russian minority.
Yet again he falls of "pop number goes up" meme to a degree comparable with 4x players and western mass immigration enthusiasts. For one i wonder how many of the people Russia gained are 60+ year olds who either were too old to move or conviced to stay by USSR nostalgia and\or prospect of Russia's higher pensions. Ukrainians often call them "Soviet people", naturally they tend to be of an age at which they are interested in pensions more than anything else. Sure, they add to numbers, but in military and economic terms their value is negligible. They won't build businesses, they won't work tech jobs, and they won't be the recruit material to replace all the lost VDV either. Obviously they also don't care that Russia's non resource economy is in shambles, they are living off a pension and they can buy their potatoes and vodka for that. Meanwhile the military and economic value of the young and middle class men who have left Russia is disproportionally high, considering Russia's demographics especially.
So ironically, Ukraine may be left with a lower, but statistically younger and far more patriotic population than before (those having doubts moving either to Russia if they lean that way politically, or to the West if they just care about money). Guess who will remain...
Also bold of him to assume that Russia will get a more competent government after Putin, and then said more competent government will continue to sacrifice it all recommitting to Putin's biggest mistake.