The way things are going, I predict that extending the requirement from 3 years to 5 will have no real effect on the incentive for players to switch to their "new" country, since if eg you're a Georgian amateur who is being offered a professional contract in England or France, for financial reasons you'll want to play there as long as you possibly can. The fact of giving up another two years playing for a country which never does anything in world rugby anyway won't cost them to lose too much sleep, I shouldn't think.
While for the big countries who do stand to benefit from such players, it just means that they will try to recruit and get them a work permit as a 20 y.o. rather than a 22 y.o., in recognition of the fact they were never certain to be regularly good enough for their "new" country until they were 25+ anyhow. While his new domestic club gets the benefit of his services earlier than ever.
Which for new country/club/player/old country is Win/Win/Win/Lose.
Or Cynical/Shabby/Understandable/Sickening.