People change denominational allegiance all the time. It isn’t as big a deal as the media sometimes makes out. If any or many among the Anglicans who can accept the full Catholic Catechism decide soon to become part of what are in effect new non-geographical Catholic dioceses, their choice will only be one among many such stories over the years.
Each of our three churches has a Treasurer. Only one was brought up in the Church of England (and I enjoy his rootedness in this expressed when asked to read at a service by always using the Authorised Version and by his gently chiding me if too many of the hymns at any Evensong are not the ones which were in use in his school chapel as a boy). One of the others was brought up as a Catholic, and was received into the Church of England a few years ago. The third was an active Methodist until quite recently, indeed a Local Preacher. And of those who have ceased to worship in the parish in my time at least one family now worships at an independent church and another with the Salvation Army.
I discovered just how wide spread this sort of movement was fifteen to twenty years ago when each year I was asked to teach a day on ecumenism for the then diocesan Local Ministry course. I would always begin by asking how many had experience of adult membership or regular childhood worship in another denomination. I never failed to get answers which covered the whole range of the main stream denominations. There was also always at least one example of something less usual (perhaps someone brought up as a Moravian or in an Orthodox church). It appears that any pool of the thirty or so committed active lay Anglicans in Lincolnshire will contain this range of denominational background, and I assume that any similarly sized pool in any other denomination is likely to contain at least one former Anglican as well.
My old colleague the Bishop of Buckingham has a Blog it is often a treat to visit and he has this very simply: ‘I’ve always thought people should serve within the denomination in which they can best be discipled; all denominations are only delivery systems for the Kingdom after all’. I’d want to sell my own brand of Christianity because I value what it has given me and what I believe it can offer others, but I do it knowing full well that selling a particular brand isn’t my primary Christian calling at all.