The proposal to kick out N-reg has been around for far longer than I have been flying, according to old hands in the business.
The implementation is incredibly difficult.
Aeroplanes have a tendency to fly, so anybody operating a fleet will just rotate it via the EU. Anybody who can rent/lease will rent for 90 days and then rent another one. The commercial opportunities there are obvious.
Anybody over 5700kg can go on the IOM register, or one of the others which accept FAA certification/licensing.
Ultimately, the only people one could really screw would be small N-reg private pilots who can only just afford to do what they currently do. These are mostly FAA IR owner/pilots, and it's pretty obvious that their total number in Europe is under 1000.
Then one has to address the very basic issue of how one could subject an aircraft operated under FAA Part 91 to EASA maintenance requirements when the aircraft itself is not EASA certified, or contains equipment (e.g. TCAS) which is not EASA certified.
This has obviously not been thought through at all, but then neither was the 2005 UK DfT proposal, which was spectacularly withdrawn the instant it got anywhere near somebody with a brain who had to think about implementing it.
I am not saying the future is cast in concrete - it isn't. Everything is fluid.
There is even a possibility (very remote) of a total ban on private (i.e. non ATPL) flight in controlled airspace under IFR. There are many old farts in aviation regulation who want this.
But it's important to keep balance and not cause undue distress to pilots, by claiming such and such is just around the corner.