Well, whatever is going to happen, if indeed it does, is bit like the budget. You'll just wake up one morning and find out that you're stuck with it.
In the case of the USA, as a general rule, if you are a citizen, regardless of whether you are a resident, you are liable for income tax on your world wide income and it takes at least ten years of physical absence to loose residence, even once your green card has expired. This catch net formula has not escaped the attention of either the HMRC or groups such as The Taxpayers Alliance, whose efforts and influence which are considerable might better be directed at the public waste rather than the public gathering. What is worrying perhaps is that HMRC have apparently obtained a ruling against a British airline at all. There seems to be little information available. HMRC have been flexing their muscles of late on residency and I note that tax avoidance, as opposed to evasion, is now considered a social crime. Tax mitigation is the buzz word for paying as little tax as you legally can. When governments start playing with the semantics you may look for some lies and hypocrisy. These are traits inherent in a socialist state such as Britain which now has an economic agenda possibly ultimately dependant upon the public sector unions, under which umbrella HMRC staff would seek refuge . The unions might need an economic scape goat or two before they bite the bullet themselves. What better victim to offer up to the green eyes than a handful of self perceived non residents who actually work for British companies, who are rich in their low tax regime and who don't vote anyway. You've seen it happen in Britain already, in the manifestos of all three parties, with so called rich foreigners and their companies. Many of both of these of course have left and will not be back under any circumstance. No one much minds paying tax not even high tax, even if it is drivelled away, but instability in tax policy is abhorrent. This is all mere idle speculation on my part but I think there is a space to watch there and a few decent enough reasons to watch it.